118-507: Eumetopias Neophoca Otaria Phocarctos Zalophus Sea lions are pinnipeds characterized by external ear flaps , long foreflippers, the ability to walk on all fours, short and thick hair, and a big chest and belly. Together with the fur seals , they make up the family Otariidae , eared seals . The sea lions have six extant and one extinct species (the Japanese sea lion ) in five genera . Their range extends from
236-977: A diagnostic agent in people with bradycardia caused by sinus node dysfunction (SND) to help correlate symptoms. Theophylline increases resting heart rate and improves subjective symptoms in most people with bradycardia due to SND. The treatment of bradycardia depends on whether the person is stable or unstable. Emergency treatment is not needed if the person is asymptomatic or minimally symptomatic. Treatment of chronic symptomatic bradycardia first necessitates correlation of symptoms. Once symptoms have been clearly linked to bradycardia, permanent cardiac pacing can be provided to increase heart rate and symptoms will improve. In people who are unwilling to undergo pacemaker implantation or are not candidates for cardiac pacing, chronic oral theophylline , an adenosine receptor antagonist , can be considered for treatment of symptomatic bradycardia. Other positive chronotropes have also been used to treat bradycardia, including
354-448: A certain threshold (so-called depolarization ) by an incoming action potential, causing the myocyte to contract . When these contractions occur in a coordinated fashion, the atria and ventricles of the heart will pump, delivering blood to the rest of the body. Normally, the origination of the action potential causing cardiomyocyte contraction originates from the sinoatrial node (SA node). This collection of specialized conduction tissue
472-539: A determining electrolytes may help determine the underlying cause. Many heathy young adults, and particularly well-trained athletes, have sinus bradycardia that is without symptoms. This can include heart rates of less than 50 or 60 bpm or even less than 40 bpm. Such individuals, without symptoms, do not require treatment. Temporal correlation of symptoms with bradycardia is necessary for diagnosis of symptomatic bradycardia. This can sometimes be difficult. Challenge with oral theophylline can be used as
590-456: A different ventricle. Finally, these bundle branches terminate in the small Purkinje fibers that innervate myocardial tissue. The His-Purkinje system conducts action potentials much faster than can be propagated between myocardial cells, allowing the entire ventricular myocardium to contract in less time, improving pump function. Most pathological causes of bradycardia result from damage to this normal cardiac conduction system at various levels:
708-410: A direct effect on their on land breeding activity. Their seasonal abundance trend correlates with their breeding period between the austral summer of January to March. Their rookeries populate with newborn pups as well as male and female otariids that remain to defend their territories. At the end of the breeding period males disseminate for food and rest while females remain for nurturing. Other points in
826-666: A given species tend to be smaller in the tropics, increase in size with increasing latitude, and reach a maximum in sub-polar regions. In a cool climate and cold waters there should be a selective advantage in the relative reduction of body surface area resulting from increased size, since the metabolic rate is related more closely to body surface area than to body weight. Sea lions, with three groups of pinnipeds, have multiple breeding methods and habits over their families but they remain relatively universal. Otariids, or eared sea lions, raise their young, mate, and rest in more earthly land or ice habitats. Their abundance and haul-out behavior have
944-414: A long period of time and prevent side effects of high pressure at depth. The high pressures associated with deep dives cause gases such as nitrogen to build up in tissues which are then released upon surfacing, possibly causing death. One of the ways sea lions deal with the extreme pressures is by limiting the amount of gas exchange that occurs when diving. The sea lion allows the alveoli to be compressed by
1062-409: A majority of thrust was produced during the drive phase of the fore flipper stroke cycle. Although previous findings on eared seals suggested that thrust was generated by the initial outward movement of the foreflippers or the terminal drag-based paddling phase, the 2007 study found that little or no thrust was generated during those phases. Swimming performance in sea lions is modulated by changes in
1180-542: A normal QRS complex accompanied by an inverted P wave either before, during, or after the QRS complex. An AV-junctional escape beat is a delayed heartbeat originating from an ectopic focus somewhere in the AV junction . It occurs when the rate of depolarization of the SA node falls below the rate of the AV node . This dysrhythmia may also occur when the electrical impulses from
1298-432: A physician is recommended, especially in the elderly. The term "relative bradycardia" can refer to a heart rate lower than expected in a particular disease state, often a febrile illness. Chronotropic incompetence (CI) refers to an inadequate rise in heart rate during periods of increased demand, often due to exercise, and is an important sign of SND and an indication for pacemaker implantation. The word "bradycardia"
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#17327727430901416-468: A possible cause of this. In contrast to cocaine however, methamphetamine has not been associated with bradyarrhythmias. Bradycardia is also part of the mammalian diving reflex . COVID-19 has been found to be a cause of bradycardia. A diagnosis of bradycardia in adults is based on a heart rate of less than 60 BPM, although some studies use a heart rate of less than 50 BPM. This is usually determined either by palpation or ECG. If symptoms occur,
1534-456: A range of vocalizations as part of their territorial behaviors, including belches, growls, snorts, and hisses that serve as warnings to others. Both males and females also produce underwater noises similar to their above water sounds, described as clicks, barks, and belches. The primary function of their vocalizations is for social behavior. Sonogram readings reported that Steller Sea Lions make discrete, low frequency pulses underwater that resemble
1652-743: A sea lion until he was rescued by the Coast Guard . Sea lions have also been a focus of tourism in Australia and New Zealand. One of the main sites to view sea lions is in the Carnac Island Nature Reserve near Perth in Western Australia. This tourist site receives over 100,000 visitors, many of whom are recreational boaters and tourists, who can watch the male sea lions haul out on to the shore. They have sometimes been called "the unofficial welcoming committee of
1770-536: A slow rate. It is a common condition found in both healthy individuals and those considered well-conditioned athletes. Studies have found that 50–85% of conditioned athletes have benign sinus bradycardia, as compared to 23% of the general population studied. The heart muscle of athletes has a higher stroke volume , requiring fewer contractions to circulate the same volume of blood. Asymptomatic sinus bradycardia decreases in prevalence with age. Sinus arrhythmias are heart rhythm abnormalities characterized by variations in
1888-623: A speed of about 30 knots (56 km/h; 35 mph). Three species, the Australian sea lion , the Galápagos sea lion and the New Zealand sea lion , are listed as endangered . Sea lions are related to walruses and seals. Together with the fur seals , they constitute the family Otariidae , collectively known as eared seals. Until recently, sea lions were grouped under a single subfamily called Otariinae, whereas fur seals were grouped in
2006-418: A speedboat. The sea lion appeared to be preparing for a second attack when the girl was rescued. An Australian marine biologist suggested that the sea lion may have viewed the girl "like a rag doll toy" to be played with. In San Francisco , where an increasingly large population of California sea lions crowds docks along San Francisco Bay, incidents have been reported in recent years of swimmers being bitten on
2124-502: A sudden AV block and dropped QRS complex. Because type 2 blocks are typically due to lesions below the AV node, the ability for ventricular escape rhythms to maintain cardiac output is compromised. Permanent pacemaker implantation is often required. An AV-junctional rhythm , or atrioventricular nodal bradycardia, is usually caused by the absence of the electrical impulse from the sinus node . This usually appears on an electrocardiogram with
2242-651: A thick mane of coarse hair around their large necks. Their Latin name translates roughly as "maned one with the broad forehead". The range of the Steller sea lion extends from the north shore of Honshu in Japan to the Gulf of Alaska in the north, down to Año Nuevo Island off the coast of central California to the south. They formerly bred as far south as the Channel Islands , but have not been observed there since
2360-448: A week births consist most usually of one pup with a perinatal period of 3 to 13 days. Steller sea lions have exhibited multiple competitive strategies for reproductive success. Sea lion mating is often polygamous as males usually mate with different females to increase fitness and success, leaving some males to not find a mate at all. Polygamous males rarely provide parental care towards the pup. Strategies used to monopolize females include
2478-421: A week or so of nursing without leaving the rookery, females begin to take progressively longer and more frequent foraging trips leaving their pups behind until at some point in late summer, when both the mother and pup leave the rookery together. This maternal attendance pattern is common in otariids. As pups get older the amount of time spent by females foraging out at sea increases. This continues until pups obtain
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#17327727430902596-451: Is 1.8 m (6 ft) long. The largest sea lions are Steller's sea lions , which can weigh 1,000 kg (2,200 lb) and grow to a length of 3.0 m (10 ft). Sea lions consume large quantities of food at a time and are known to eat about 5–8% of their body weight (about 6.8–15.9 kg (15–35 lb)) at a single feeding. Sea lions can move around 16 knots (30 km/h; 18 mph) in water and at their fastest they can reach
2714-437: Is certainly due to a complex of interrelated factors which have yet to be defined by the research effort. Another possible reason for decline in this species has been tied to the nutritional stress hypothesis. The lack of prey corresponds to the decrease in population. In females specifically, obtaining an insufficient amount of nutrients has resulted in the failure to complete their pregnancies to full term. In October 2013,
2832-406: Is commonly due to structural heart disease, myocardial ischemia, or age-related fibrosis. Atrioventricular blocks are divided into three categories, ranked by severity. AV block is diagnosed via surface ECG, which is usually sufficient to locate the causal lesion of the block without the need for an invasive electrophysiology study . In 1st degree AV block , electrical impulses originating in
2950-472: Is from the Greek βραδύς bradys "slow", and καρδία kardia "heart". The heart is a specialized muscle containing repeating units of cardiomyocytes , or heart muscle cells. Like most cells, cardiomyocytes maintain a highly regulated negative voltage at rest and are capable of propagating action potentials , much like neurons. While at rest, the negative cellular voltage of a cardiomyocyte can be raised above
3068-452: Is generally reserved for patients with symptoms, regardless of minimum heart rate during sleep or the presence of concomitant heart rhythm abnormalities (See: Sinus pause ), which are common with this condition. Untreated SND has been shown to increase the future risk of heart failure and syncope, sometimes warranting definitive treatment with an implanted pacemaker . In atrioventricular causes of bradycardia, permanent pacemaker implantation
3186-557: Is greater than that of SA blocks. A variety of medications can induce or exacerbate bradycardia. These include beta blockers like propranolol , calcium channel blockers like verapamil and diltiazem , cardiac glycosides like digoxin , alpha-2 agonists like clonidine , and lithium , among others. Beta blockers may slow the heart rate to a dangerous level if prescribed with calcium channel blockers. Chronic cocaine use has been associated with bradycardia. Desensitization of β-adrenergic receptors has been suggested as
3304-460: Is located in the right atrium, near the entrance of the superior vena cava . The SA node contains pacemaker cells that demonstrate "automaticity" and can generate impulses that travel through the heart and create a steady heartbeat. At the beginning of the cardiac cycle, the SA node generates an electrical action potential that spreads across the right and left atria , causing the atrial contraction of
3422-473: Is more commonly seen in fatty acid oxidation disorders , acute bradycardia can occur more rarely. Cardiac causes include acute or chronic ischemic heart disease , vascular heart disease, valvular heart disease , or degenerative primary electrical disease. Ultimately, the causes act by three mechanisms: depressed automaticity of the heart, conduction block, or escape pacemakers and rhythms. In general, two types of problems result in bradycardias: disorders of
3540-498: Is often required when no reversible causes of disease are found. In both SND and atrioventricular blocks, there is little role for medical therapy unless a patient is hemodynamically unstable , which may require the use of medications such as atropine and isoproterenol and interventions such as transcutenous pacing until such time that an appropriate workup can be undertaken and long-term treatment selected. While asymptomatic bradycardias rarely require treatment, consultation with
3658-470: Is present and is the cause of symptomatic bradycardia, symptoms respond well to replacement therapy with thyroid hormone . Discontinuation of medications that induce or exacerbate bradycardia, such as beta blockers , calcium channel blockers , sodium channel blockers , and potassium channel blockers , can improve symptoms. If discontinuation of these medications is not possible due to clinical need, cardiac pacing can be considered with continuation of
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3776-462: Is prohibited, but limited hunting permits are occasionally granted for First Nations communities, or if local culling is deemed necessary, for example, nuisance animals destroying fish farms. In recent years, Steller sea lions have been known to enter the Columbia River estuary and feed on white sturgeon , several salmon species, and rainbow trout , some of which are also listed under
3894-628: The Commander Islands belong to the western stock. In the summer, Steller sea lions tend to shift their range somewhat southward. Therefore, though there are no reproductive rookeries in Japan, several consistent haul-out sites are found around Hokkaidō in the winter and spring. Vagrants have been spotted in the Yellow Sea and Bohai Gulf and along the coast of the Korean Peninsula and China. The oldest fossil known of
4012-625: The Galápagos Islands ". [REDACTED] Eumetopias The Steller sea lion ( Eumetopias jubatus ), also known as Steller's sea lion or the northern sea lion , is a large, near-threatened species of sea lion, predominantly found in the coastal marine habitats of the northeast Pacific Ocean and the Pacific Northwest regions of North America , from north-central California to Oregon , Washington and British Columbia to Alaska . Its range continues across
4130-757: The Northern Pacific and the Aleutian Islands , all the way to Kamchatka , Magadan Oblast , and the Sea of Okhotsk , south to Honshu 's northern coastline. It is the sole member of the genus Eumetopias , and the largest of the so-called eared seals (Otariidae). Among pinnipeds , only the walrus and the two species of elephant seal are bigger. The species is named for the naturalist and explorer Georg Wilhelm Steller , who first described them in 1741. Steller sea lions have attracted considerable attention in recent decades, both from scientists and
4248-480: The cardiac cycle . This electrical impulse carries on to the atrioventricular node (AV node), another specialized grouping of cells located in the base of the right atrium, which is the only anatomically normal electrical connection between the atria and ventricles. Impulses coursing through the AV node are slowed before carrying on to the ventricles, allowing for appropriate filling of the ventricles before contraction. The SA and AV nodes are both closely regulated by
4366-770: The etiology of the slow heart rate, classified by the anatomic location of a dysfunction within the cardiac conduction system . Generally, these classifications involve the broad categories of sinus node dysfunction (SND), atrioventricular block, and other conduction tissue diseases. However, bradycardia can also result without dysfunction of the native conduction system, arising secondary to medications including beta blockers , calcium channel blockers , antiarrythmics , and other cholinergic drugs. Excess vagus nerve activity or carotid sinus hypersensitivity are neurological causes of transient symptomatic bradycardia. Hypothyroidism and metabolic derangements are other common extrinsic causes of bradycardia. The management of bradycardia
4484-455: The subarctic to tropical waters of the global ocean in both the Northern and Southern Hemispheres , with the notable exception of the northern Atlantic Ocean . They have an average lifespan of 20–30 years. A male California sea lion weighs on average about 300 kg (660 lb) and is about 2.4 m (8 ft) long, while the female sea lion weighs 100 kg (220 lb) and
4602-428: The vasodilator and antihypertensive agent hydralazine , the alpha-1 blocker prazosin , anticholinergics , and sympathomimetic agents like beta-1 agonists . However, side effects , like orthostatic hypotension with hydralazine, prazosin, and anticholinergics and myocardial toxicity with sympathomimetics, as well as limited data for this indication, hinder their routine and long-term use. If hypothyroidism
4720-598: The 1980s. Based on genetic anаlyses and local migration patterns, the global Steller sea lion population has traditionally been divided into an eastern and western stock at 144°W longitude, roughly through the middle of the Gulf of Alaska. Recent evidence suggests the sea lions in Russia in the Sea of Okhotsk and the Kuril Islands comprise a third Asian stock, while the sea lions on the eastern seaboard of Kamchatka and
4838-469: The 19th century their whiskers sold for a penny apiece for use as tobacco- pipe cleaners . Steller sea lions are sometimes killed intentionally by fishermen, as they are seen as competitors and a threat to fish stocks. Killing sea lions is strictly prohibited in the US and Russia; however, in Japan, a fixed number are still harvested annually, ostensibly to protect their fisheries. In Canada, commercial hunting
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4956-573: The AV node will produce a wide QRS complex with heart rates between 20 and 40 BPM. Those above the bundle of His, also known as junctional, will typically range between 40 and 60 BPM with a narrow QRS complex. In a third-degree heart block , about 61% take place at the bundle branch-Purkinje system, 21% at the AV node, and 15% at the bundle of His. AV block may be ruled out with an ECG indicating "a 1:1 relationship between P waves and QRS complexes." Ventricular bradycardias occurs with sinus bradycardia, sinus arrest, and AV block. Treatment often consists of
5074-461: The Chilean coast with a population estimate of 165,000. According to the most recent surveys in northern and southern Chile the sealing period of the middle twentieth century that left a significant decline in sea lion population is recovering. The recovery is associated with less hunting, otariids rapid population growth, legislation on nature reserves, and new food resources. Haul-out patterns change
5192-596: The Galapagos Islands, but in addition, the researchers in Australia took blood samples. The pups in Australia were being affected by hookworms, but they were also coming out in large numbers with warmer temperatures. New Zealand sea lion pups ( Phocarctos hookeri ) were also affected in really early ages by hookworms (Uncinaria). The difference is that in New Zealand researchers took the necessary steps and began treatment. The treatment seemed to be effective on
5310-541: The PR interval shortening again to baseline. Type 1 2nd degree AV block due to disease in the AV node (as opposed to in the His-purkinje system) rarely needs intervention with pacemaker implantation. 2nd degree, Mobitz type 2 AV block is another phenomenon of intermittently dropped QRS complexes after characteristic groupings of beats seen on surface ECG. The PR and RR intervals are consistent in this condition, followed by
5428-420: The SA node (or other ectopic focus above the ventricles) are conducted with significant delay through the AV node. This condition is diagnosed via ECG, with PR intervals in excess of 200 milliseconds. The PR interval represents the length of time between the start of atrial depolarization and the start of ventricular depolarization, representing the flow of electrical impulses between the SA and AV nodes. Despite
5546-432: The SA node and disorders of the AV node. With SA node dysfunction (sometimes called sick sinus syndrome), there may be disordered automaticity or impaired conduction of the impulse from the SA node into the surrounding atrial tissue (an "exit block"). Second-degree sinoatrial blocks can be detected only by use of a 12-lead ECG. It is difficult and sometimes impossible to assign a mechanism to any particular bradycardia, but
5664-417: The SA node and the ventricles. 2nd degree block is classified into two types. Mobitz type 1 block, otherwise known by the eponym Wenckebach , classically demonstrates grouped patterns of heartbeats on ECG. Throughout the group, the PR interval gradually lengthens until a dropped conduction occurs, resulting in no QRS complex seen on surface ECG following the last P wave. After a delay, the grouping repeats, with
5782-446: The SA node fail to reach the AV node because of SA or AV block. This is a protective mechanism for the heart to compensate for an SA node that is no longer handling the pacemaking activity and is one of a series of backup sites that can take over pacemaker function when the SA node fails to do so. This would present with a longer PR interval . An AV-junctional escape complex is a normal response that may result from excessive vagal tone on
5900-402: The SA node. Pathological causes include sinus bradycardia, sinus arrest, sinus exit block, or AV block. Idioventricular rhythm , also known as atrioventricular bradycardia or ventricular escape rhythm, is a heart rate of less than 50 BPM. This is a safety mechanism when a lack of electrical impulse or stimuli from the atrium occurs. Impulses originating within or below the bundle of His in
6018-782: The U.S. Endangered Species Act . They are found in the Columbia River nearly year round, with the exception of early summer, going as far upstream as Bonneville Dam . Though not as abundant as the California sea lion , there is still concern amongst agencies tasked with managing and monitoring the fish populations; as the Steller sea lions are, themselves, protected under the Marine Mammal Protection Act , managers are implored to use non-harmful, non-lethal deterrence methods (such as rubber bullets, bullhorns and other noisemakers). Interference or deterrence by
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#17327727430906136-624: The abundance of sea lions at particular times of the day, month, and year. Patterns in migration relate to temperature, solar radiation, and prey and water resources. Studies of South American sea lions and other otariids document maximum population on land during early afternoon, potentially due to haul-out during high air temperatures. Adult and subadult males do not show clear annual patterns, maximum abundance being found from October to January. Females and their pups hauled-out during austral winter months of June to September. South American sea lions have been greatly impacted by human exploitation. During
6254-417: The administration of atropine and cardiac pacing . For infants, bradycardia is defined as a heart rate less than 100 BPM (normal is around 120–160 BPM). Premature babies are more likely than full-term babies to have apnea and bradycardia spells; their cause is not clearly understood. The spells may be related to centers inside the brain that regulate breathing which may not be fully developed. Touching
6372-849: The amount of time that Steller sea lions spend on land. Haul-out sites and haul-out abundance of the Steller sea lion can be determined by prey availability, predator abundance, tide levels, weather, etc. Steller sea lions are skilled and opportunistic marine predators, feeding on a wide range of fish and cephalopod species. Important diet components include walleye pollock , Atka mackerel , halibut , herring , capelin , flatfish Pacific cod , rockfish , sculpins , salmon, sand lance, and cephalopods such as various squid and octopus. They seem to prefer schooling fish and forage primarily between intertidal zones and continental shelves . They usually aggregate in groups of up to twelve in areas of prey abundance. They are known to aggregate near fishing vessels, preying on bycatch discards. Most of
6490-416: The animal know its available oxygen supply. Yet, the sea lions cannot avoid the effects of gradual CO 2 build-up which eventually causes the sea lions to spend more time at the surface after multiple repeated dives to allow for enough built up CO 2 to be expired. Galapagos sea lions ( Zalophus wollebaeki ) can be infected with Philophthalmus zalophi , an eye fluke. These infections have heavy impacts on
6608-487: The autonomic nervous system's fibres, allowing for adjustment of cardiac output by the central nervous system in times of increased metabolic demand. Following slowed conduction through the atrioventricular node, the action potential produced initially at the SA node now flows through the His-Purkinje system. The bundle of His originates in the AV node and rapidly splits into a left and right branch, each destined for
6726-651: The baby gently or rocking the incubator slightly will almost always get the baby to start breathing again, which increases the heart rate. The neonatal intensive-care unit standard practice is to electronically monitor the heart and lungs. Bradycardia arrhythmia may have many causes, both cardiac and non-cardiac. Non-cardiac causes are usually secondary and can involve recreational drug use or abuse , metabolic or endocrine issues, especially hypothyroidism , an electrolyte imbalance , neurological factors, autonomic reflexes , situational factors, such as prolonged bed rest , and autoimmunity . At rest, although tachycardia
6844-453: The beginning of January through the month of May and lower temperatures throughout the rest of the year. Parasites surfaced in large numbers when the sea temperature was at its highest. Furthermore, data was collected by capturing sea lions in order to measure and determine their growth rates. Their growth rates were noted along with the citings of parasites which were found under the eyelid. The shocking results were that sea lions are affected by
6962-435: The bleats of sheep, and bellows. Because Steller sea lions are sexually dimorphic in size, their hearing differs in sensitivity, possibly due to differences in size of the hearing structures. Females have a higher sensitivity than males, perhaps to hear the higher frequency calls of their pups. The Steller sea lion's hearing range also suggests that they are capable of hearing the underwater calls of one of their main predators,
7080-461: The blood, due to the unloading complications with CO 2 . However, having more than normal levels of CO 2 in the blood does not seem to adversely affect dive behavior. Compared to terrestrial mammals, sea lions have a higher tolerance to storing CO 2 which is what normally tells mammals that they need to breathe. This ability to ignore a response to CO 2 is likely brought on by increased carotid bodies which are sensors for oxygen levels that let
7198-438: The cardiac cycle length over 120 milliseconds (longest cycle - shortest cycle). These are the most common type of arrhythmia in the general population and usually have no significant consequences. They typically occur in the young, athletes or after administration of medications such as morphine. The types of sinus arrhythmia are separated into the respiratory and non-respiratory categories. Respiratory sinus arrhythmia refers to
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#17327727430907316-575: The data on their foraging comes from data collected off the coast of Alaska; little is known of their foraging behavior elsewhere. The composition of the diet of Steller sea lions varies seasonally and geographically; as opportunistic predators, they concentrate on the locally most abundant prey species. In addition to their primary marine environment, they sometimes enter estuaries and feed on brackish-water fish such as sturgeon . Very occasionally, they have been known to prey on northern fur seals , harbor seals , and sea otter pups. Records suggest that
7434-485: The decline in Steller sea lions common to Alaska. The largest of the eared seals, Steller sea lions are quick swimmers, about as fast as the smaller California sea lions . Glide velocity of individual Steller sea lions has been measured as 2.9–3.4 meters or 1.2–1.5 body lengths per second, which is close to the optimal swim velocity of 1.4 body lengths per second based on the minimum cost of transport for California sea lions. A 2007 study of Steller sea lions found that
7552-403: The drastic effects humans have on their ecosystems. As a result, South American sea lions have been foraging at higher tropical latitudes than they did prior to human exploitation. Fishermen play a key role in the endangerment of sea lions. Sea lions rely on fish, like pollock, as a food source and have to compete with fishermen for it. When fishermen are successful at their job, they greatly reduce
7670-698: The duration and intensity of movements without changing their sequence. Using criteria based on velocity and the minimum radius of turns, Steller sea lions' maneuverability is similar to that of other eared seals, superior to that of cetaceans, and inferior to that of many fish. To be able to dive for a long period of time, Steller sea lions exhibit apnea , bradycardia , and peripheral vasoconstriction . This allows them to maximize their oxygen stores and efficiently forage during their dives. In addition to those adaptations, their thick blubber layer and outer fur layer keep their body insulated during dives. Trained Steller sea lions from Vancouver Aquarium were placed in
7788-715: The eastern Steller sea lion was taken off the U.S. Endangered Species List after a major population comeback over the past several years. [REDACTED] Bradycardia Bradycardia , also called bradyarrhythmia , is a resting heart rate under 60 beats per minute (BPM). While bradycardia can result from various pathologic processes, it is commonly a physiologic response to cardiovascular conditioning or due to asymptomatic type 1 atrioventricular block . Resting heart rates of less than 50 BPM are often normal during sleep in young and healthy adults and athletes . In large population studies of adults without underlying heart disease, resting heart rates of 45-50 BPM appear to be
7906-421: The family into the subfamilies Arctocephalinae (fur seals) and Otariinae (sea lions) is not supported, with the fur seal Callorhinus ursinus having a basal relationship relative to the rest of the family. This is consistent with the fossil record which suggests that this genus diverged from the line leading to the remaining fur seals and sea lions about 6 million years ago (mya). Similar genetic divergences between
8024-404: The fertility rate by far. Since most pups are unable to reach the age of reproduction, the population is not growing fast enough to keep the species out of endangerment. Other parasites, like Anisakis and heartworm , can also infect sea lions. Australian sea lions ( Neophoca cinerea ) are also being affected by more frequent parasitic infections. The same method was used for the sea pups as on
8142-795: The fifth year, after which female growth slows considerably. Adult females measure 2.3–2.9 m (7.5–9.5 ft) in length, on average being 2.5 m (8.2 ft), and weigh 240–350 kg (530–770 lb), with an average of 263 kg (580 lb). Males continue to grow until their secondary sexual traits appear in their fifth to eighth year. Males are slightly longer than the females, growing to about 2.82–3.25 m (9.3–10.7 ft) long and averaging 3 m (9.8 ft) in length. Males have much wider chests, necks, and general forebody structure. Males can weigh between 450–1,120 kg (990–2,470 lb), weighing on average 544 kg (1,199 lb). Males are further distinguished from females by broader and higher foreheads, flatter snouts, and
8260-589: The first time, and since then, they have slowly been recolonizing. These sea lions are the only pinnipeds that regularly move up to 2 kilometres (1.2 mi) inland into forests. As consequence, they have been hit by cars on roads, deliberately killed, and been disturbed by dogs. Females need to move inland as a way to protect their pups, so roads, fences, residential areas, and private lands can inhibit their dispersal and breeding success. They have also adapted to commercial pine forests, and have given birth or nursed pups in residents' backyards and on golf courses. As one of
8378-450: The fur, generally smaller sizes, farther and longer foraging trips, smaller and more abundant prey items, and greater sexual dimorphism . All sea lions have certain features in common, in particular their coarse, short fur, greater bulk, and larger prey than fur seals. For these reasons, the distinction remains useful. The family Otariidae (Order Carnivora) contains the 15 extant species of fur seals and sea lions. Traditional classification of
8496-424: The general public is unlawful, unregulated, and considered to be stressful (even disruptive) to the animals and their habits. Additionally, the massive size of the Steller sea lion—and potential for aggression—poses a real threat for humans; thus, the interfering with, molestation or frightening of marine mammals is strictly forbidden. Offenders are subject to varying fines, court appearances and even jail time. While
8614-509: The general public, due to significant (and largely unexplained) declines in their numbers over an extensive portion of their northern range, notably in Alaska. Adult animals are lighter in color than most sea lions, ranging from pale yellow to tawny and occasionally reddish. Steller sea lion pups are born almost black, weighing around 23 kg (51 lb), and remain dark in coloration for several months. Females and males both grow rapidly until
8732-532: The ideal body weight and energy reserves to eat on their own. A study conducted by the University of California, Santa Cruz found that on average male pups consume more milk than females. This may be due to the sexual dimorphism common to otariids. Reproductive males fast throughout the reproductive season, often without entering the water once from mid-May until August, when the structure of the reproductive rookeries begins to fall apart and most animals leave for
8850-489: The increasing water pressure thus forcing the surface air into cartilage lined airway just before the gas exchange surface. This process prevents any further oxygen exchange to the blood for muscles, requiring all muscles to be loaded with enough oxygen to last the duration of the dive. However, this shunt reduces the amount of compressed gases from entering tissues therefore reducing the risk of decompression sickness. The collapse of alveoli does not allow for any oxygen storage in
8968-458: The killer whale. Steller sea lion were hunted for meat and other commodities by prehistoric communities everywhere their range intersected with human communities. Aside from food and clothing, their skin was used to cover baidarkas and kayaks . A subsistence harvest on the order of 300 animals or less continues to this day in some native communities in Alaska. Historically, the sea lion has had only very slight commercial value. For example, in
9086-463: The late Holocene period to the middle of the twentieth century, hunter-gatherers along the Beagle Channel and northern Patagonia had greatly reduced the number of sea lions due to their hunting of the species and exploitation of the species' environment. Although sealing has been put to a halt, in many countries, such as Uruguay , the sea lion population continues to decline because of
9204-531: The legs by large, aggressive males, possibly as territorial acts . In April 2015, a sea lion attacked a 62-year-old man who was boating with his wife in San Diego . The attack left the man with a punctured bone. In May 2017, a sea lion grabbed and pulled a girl into the water by her dress before retreating. The child was sitting on a pier side in British Columbia while tourists were illegally feeding
9322-429: The lower limits of normal, dependent on age and sex. Bradycardia is most likely to be discovered in the elderly, as age and underlying cardiac disease progression contribute to its development. Bradycardia may be associated with symptoms of fatigue , dyspnea , dizziness , confusion , and frank syncope due to reduced forward blood flow to the brain, lungs, and skeletal muscle. The types of symptoms often depend on
9440-445: The lungs, however. This means that sea lions must mitigate oxygen use in order to extend their dives. Oxygen availability is prolonged by the physiological control of heart rate in sea lions. By reducing heart rate to well below surface rates, oxygen is saved by reducing gas exchange as well as reducing the energy required for a high heart rate. Bradycardia is a control mechanism to allow a switch from pulmonary oxygen to oxygen stored in
9558-461: The male "belching" territorial noise made in air. These underwater vocalizations have an average of 20–30 pulses per second. Vocalizations are critical to mother-pup pairs, as the mothers must find their pups in a crowded breeding area when they return from foraging. The mother and pup both use distinctive calls, like names, to help differentiate themselves among the crowd of other sea lions. Their aerial vocalizations have been described as similar to
9676-430: The medications. Beta blockers with intrinsic sympathomimetic activity (i.e., partial agonist activity), like pindolol , have less risk of bradycardia and may be useful as replacements of pure beta blockers, like propranolol , atenolol , and metoprolol . If a person is unstable, the initial recommended treatment is intravenous atropine . Doses less than 0.5 mg should not be used, which may further decrease
9794-424: The most success in defending them. The boundaries are defined by natural features, such as rocks, faults, or ridges in rocks, and territories can remain stable for 60 days. Though Steller sea lion males are generally tolerant of pups, one male filmed on Medny Island in Russia was documented killing and eating several pups in a first-ever recorded incident of cannibalism . Though researchers are uncertain as to
9912-497: The motives or reasons behind said attacks, it is suggested that the bull involved may have an abnormal personality akin to being psychotic. Pregnant females give birth soon after arriving on a rookery, and copulation generally occurs one to two weeks after giving birth, but the fertilized egg does not become implanted in the uterus until the fall. A fertilized egg may remain in embryonic diapause for up to three months before implanting and beginning to divide. Twins are rare. After
10030-433: The muscles which is needed when the sea lions are diving to depth. Another way sea lions mitigate the oxygen obtained at the surface in dives is to reduce digestion rate. Digestion requires metabolic activity and therefore energy and oxygen are consumed during this process; however, sea lions can limit digestion rate and decrease it by at least 54%. This reduction in digestion results in a proportional reduction in oxygen use in
10148-546: The native sinus node itself and are frequently accompanied by damaged AV node conduction and reduced backup pacemaker activity. The condition can also be caused by dysfunction of the autonomic nervous system that regulates the node and is commonly exacerbated by medications. Bradycardia can also result from the inhibition of the flow of action potentials through the atrioventricular (AV) node. While this can be normal in young patients due to excessive vagus nerve tone, symptomatic bradycardia due to AV node dysfunction in older people
10266-706: The node, preventing or delaying atrial depolarization and subsequent ventricular systole. Therefore, the length of the pause in heartbeats is usually a multiple of the P-P interval, as seen on electrocardiography. Like a sinus pause, a sinoatrial exit block can be symptomatic, especially with prolonged pause length. A syndrome of intrinsic disease of the sinus node, referred to as sick sinus syndrome or sinus node dysfunction , covers conditions that include symptomatic sinus bradycardia or persistent chronotropic incompetence, sinoatrial block , sinus arrest , and tachycardia-bradycardia syndrome. These conditions can be caused by damage to
10384-748: The object of intense study and the focus of much political and scientific debate in Alaska . One suspected cause of their precipitous decline was the overfishing of Alaska pollock , herring , and other fish stocks in the Gulf of Alaska. This stems largely from the "junk-food hypothesis" representing a shift in their diet from fatty herring and capelin to leaner fare such as pollock and flounder, thereby limiting their ability to consume and store fat. Other hypotheses include increased predation by orcas and sharks, indirect effects of prey species composition shifts due to changes in climate, effects of disease or contaminants, shooting by fishermen, and others. The decline
10502-445: The observations of skulls of several Otariidae species; a general change in size corresponds with a change in latitude and primary productivity. Skulls of Australian sea lions from Western Australia were generally smaller in length whereas the largest skulls are from cool temperate localities. Otariidae are in the process of species divergence, much of which may be driven by local factors, particularly latitude and resources. Populations of
10620-675: The oceans. These toxins are ingested by sardines and other fish which are then eaten by the sea lions, causing neurological damage and diseases such as epilepsy. Gene expressions are being used more often to detect the physiological responses to nutrition, as well as other stressors. In a study done with four Steller sea lions (Eumetopias jubatus), three of the four sea lions underwent a 70-day trial which consisted of unrestricted food intake, acute nutritional stress, and chronic nutritional stress. Results showed that individuals under nutritional stress down-regulated some cellular processes within their immune response and oxidative stress. Nutritional stress
10738-415: The open ocean at the University of British Columbia's Open Water Research Station to study their diving metabolism and behavior. Steller sea lions' dives are more energetically costly if they perform dive bouts. The aerobic diving limit of Steller sea lions was observed to be affected by their nutritional state and feeding. Like most otariids, Steller sea lions are vocal in air. Mature male sea lions have
10856-415: The open seas and disperse throughout their range. The age at weaning is highly variable; pups may remain with their mothers for as long as four years. Incidents of mothers feeding daughters that are simultaneously feeding their own newborn pups have been documented, which is an extremely rare occurrence among mammals. A study done at Año Nuevo in 1983 found that female attendance and time spent with their pup
10974-411: The parasites from the early ages of 3 weeks old up until the age of 4 to 8 months. The parasites found in the eye fluke did serious damage to the eye. From the data collected, 21 of the 91 survived; with a total of 70 deaths in just a span of two years. The parasites are attacking the pups at such young ages and causing the pups to not reach the age of reproduction. The death rates of the pups is surpassing
11092-488: The physiologically normal variation in heart rate due to breathing. During inspiration, vagus nerve activity decreases, reducing parasympathetic innervation of the sinoatrial node and causing an increase in heart rate. During expiration, heart rates fall due to the converse occurring. Non-respiratory causes of sinus arrhythmia include sinus pause, sinus arrest , and sinoatrial exit block . Sinus pause and arrest involve slowing or arresting of automatic impulse generation from
11210-503: The populations of the eastern and Asian stocks appear stable, the population of the western stock, particularly along the Aleutian Islands , was estimated to have fallen by 70–80% since the 1970s. As a consequence, in 1997 the western stock of Steller sea lions was listed as endangered and the eastern stock was listed as threatened under the United States Endangered Species Act . They have since been
11328-891: The presence of double rooted cheek teeth and is thus thought to represent the most "primitive" line. It was from this basal line that both the sea lions and the remaining fur seal genus, Callorhinus , are thought to have diverged. The fossil record from the western coast of North America presents evidence for the divergence of Callorhinus about 6 mya, whereas fossils in both California and Japan suggest that sea lions did not diverge until years later. There are many components that make up sea lion physiology and these processes control aspects of their behavior. Physiology dictates thermoregulation, osmoregulation, reproduction, metabolic rate, and many other aspects of sea lion ecology including but not limited to their ability to dive to great depths. The sea lions' bodies control heart rate, gas exchange, digestion rate, and blood flow to allow individuals to dive for
11446-581: The pups who have taken it. They found no traces of this infection afterwards. However, the percentage of pups who do have it is still relatively high at about 75%. Those pups who were treated had much better growth rates than those who did not. Overall parasites and hookworms are killing off enough pups to place them in endangerment. Parasites affect sea pups in various areas of the world. Reproductive success reduces immensely, survival methods, changes in health and growth have also been affected. Similarly, climate change has resulted in increased toxic algae blooms in
11564-429: The pups' milk intake had a direct relationship to their size. Pups that consumed more milk were heavier than those that did not. These findings show that the amount of time females spend onshore with their pups is based on their pup's suckling efficiency and nutritional demands. In the past, the low pup production has been tied to an increase in nutritional stress found in females. This was believed to have contributed to
11682-502: The range of their prey species has broadened over time. Steller sea lions are top-tier carnivores, but are susceptible to predation, primarily by killer whales . Shark species are also possible predators: sleepers and great whites may prey on juvenile sea lions. Reproductively mature male sea lions gather together mid-spring on traditional, well-defined reproductive rookeries , usually on beaches on isolated islands. The larger, older males establish and defend distinct territories on
11800-416: The resource-defense polygyny, or occupying important female resources. This involves occupying and defending a territory with resources or features attractive to females during sexually receptive periods. Some of these factors may include pupping habitat and access to water. Other techniques include potentially limiting access of other males to females. Otaria flavescens (South American sea lion) lives along
11918-497: The rookery. A week or so later, adult females arrive, accompanied occasionally by sexually immature offspring, and form fluid aggregations throughout the rookery. Like all other otariids , Steller sea lions are polygynous . However, unlike some other species, they do not coerce individual females into harems, but control spatial territories among which females freely move. Steller sea lions have used aquatic, semiaquatic, and terrestrial territories. Males with semiaquatic territories have
12036-455: The sea lion clades as well as between the major Arctocephalus fur seal clades, suggest that these groups underwent periods of rapid radiation at about the time they diverged from each other. The phylogenetic relationships within the family and the genetic distances among some taxa highlight inconsistencies in the current taxonomic classification of the family. Arctocephalus is characterized by ancestral character states such as dense underfur and
12154-412: The sea lion's food source, which in turn endangers the species. Also, human presence and human recreational activities can cause sea lions to engage in violent and aggressive actions. When humans come closer than 15 meters of a sea lion, the sea lions' vigilance increases because of the disturbance of humans. These disturbances can potentially cause sea lions to have psychological stress responses that cause
12272-409: The sea lions to retreat, sometimes even abandon their locations, and decreases the amount of time sea lions spend hauling out. New Zealand sea lions were also exploited from hunting and sealing, and as a result were extirpated from New Zealand's mainland for over 150 years, with their population being restricted to the subantarctic. In 1993, a female New Zealand sea lion gave birth on the mainland for
12390-542: The sea lions when the incident took place. She was pulled out of the water with minor injuries and received antibiotic prophylactic treatment for seal finger infection from the superficial bite injury. There have also been documented events of sea lions assisting humans. One such notable instance of this is when Kevin Hines jumped off the Golden Gate Bridge in a suicide attempt and was helped to stay afloat by
12508-401: The sinoatrial node, the atrioventricular node, or damage to conduction tissue between or after these nodes. Bradycardia caused by the alterations of sinus node activity is divided into three types. Sinus bradycardia is a sinus rhythm of less than 50 BPM. Cardiac action potentials are generated from the SA node and propagated through an otherwise normal conduction system, but they occur at
12626-406: The sinus node. This can lead to asystole or cardiac arrest if ventricular escape rhythms do not create backup sources of cardiac action potentials. Sinoatrial exit block is a similar non-respiratory phenomenon of temporarily lost sinoatrial impulses. However, in contrast to a sinus pause, the action potential is still generated at the SA node but is either unable to leave or delayed from leaving
12744-400: The species was found near Kanazawa , Japan and dates to the late Early Pleistocene , approximately 800,000 years ago. Steller sea lions tend to live in the coastal waters of the subarctic because of the cooler temperate climate of the area. Like all otariids , Steller sea lions are amphibious and spend some time in water and some on land. Typically, Stellar sea lions spend their time in
12862-407: The stomach and therefore a correlated oxygen supply for diving. Digestion rate in these sea lions increases back to normal rates immediately upon resurfacing. Oxygen depletion limits dive duration, but carbon dioxide (CO 2 ) build-up also plays a role in the dive capabilities of many marine mammals . After a sea lion returns from a long dive, CO 2 is not expired as fast as oxygen is replenished in
12980-545: The subfamily Arcocephalinae. This division was based on the most prominent common feature shared by the fur seals and absent in the sea lions, namely the dense underfur characteristic of the former. Recent genetic evidence, suggests Callorhinus , the genus of the northern fur seal , is more closely related to some sea lion species than to the other fur seal genus, Arctocephalus . Therefore, the fur seal/sea lion subfamily distinction has been eliminated from many taxonomies. Nonetheless, all fur seals have certain features in common:
13098-445: The survival of juveniles. The disease appears to be compounded by global warming. The number of infectious stages of different parasites species has a strong correlation with temperature change, therefore it is essential to consider the correlation between the increasing number of parasitic infections and climate changes. The Galapagos Islands go through seasonal changes in sea surface temperatures , which consist of high temperatures from
13216-454: The term "block," no impulses are fully lost in this conduction but are merely delayed. The location of the causal lesion can be anywhere between the AV node and the His-Purkinje system but is most commonly found in the AV node itself. Generally, isolated PR prolongation in 1st degree AV block is not associated with increased mortality or hospitalization. 2nd degree AV block is characterized by intermittently lost conduction of impulses between
13334-437: The underlying mechanism is not clinically relevant to treatment, which is the same in both cases of sick sinus syndrome: a permanent pacemaker . AV conduction disturbances (AV block; primary AV block , secondary type I AV block , secondary type II AV block , tertiary AV block ) may result from impaired conduction in the AV node or anywhere below it, such as in the bundle of His. The clinical relevance pertaining to AV blocks
13452-616: The water feeding but haul-out onto land to reproduce, raise their pups, molt , and rest. Steller sea lions usually congregate on isolated islands because they are the ideal terrestrial habitat. These isolated islands are preferred by Stellar sea lions because they can avoid predation from terrestrial predators, easily thermoregulate (by means of cooling winds), and access offshore prey more easily. Some haul-out sites, known as rookeries , are commonly used for reproduction while other haul-out sites are used for other purposes like molting. However, both biotic and abiotic factors can influence
13570-483: The world's rarest sea lions, and an endangered and endemic species, efforts are being made to facilitate coexistence between them and humans. Sea lion attacks on humans are rare, but when humans come within approximately 2.5 meters (8 ft), it can be very unsafe. In a highly unusual attack in 2007 in Western Australia , a sea lion leapt from the water and seriously mauled a 13-year-old girl surfing behind
13688-504: The year consist of a mix of ages and genders in the rookeries with haul-out patterns varying monthly. Steller sea lions, living an average of 15 to 20 years, begin their breeding season when adult males establish territories along the rookeries in early May. Male sea lions reach sexual maturity from ages 5 to 7 and do not become territorial until around 9 to 13 years of age. The females arrive in late May bringing in an increase of territorial defense through fighting and boundary displays. After
13806-678: Was considered the most proximate cause of population decline in this species. In New Zealand sea lions, north-to south gradients driven by temperature differences were shown to be key factors in the prey mix. Adult California sea lions eat about 5% to 8% of their body weight per day (15–40 lb (6.8–18.1 kg)). California sea lions feed mainly offshore in coastal areas. They eat a variety of prey—such as squid, anchovies, mackerel, rockfish, and sardines—found in upwelling areas. They also may take fish from commercial fishing gear, sport fishing lines, and fish passage facilities at dams and rivers. Geographic variation for sea lions have been determined by
13924-541: Was shaped by increasing nutritional demands of the pup and the pups suckling efficiency. Females averaged 21 hours ashore and 36 hours at sea. As the pups aged, females began to spend more time at sea again. As the pups matured, specifically at the sixth week past birth, the mother's sea time declined by 30 percent. There was no relationship between the pups' activity or physical excursion and their suckling time, age, or sex. Their suckling time, and age, and sex are unrelated to their use of energy. Labeled water studies showed that
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