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Hauling-out is a
behaviour Behavior (American English) or behaviour (British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as wel ...
associated with
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the walru ...
s (
true seals The earless seals, phocids or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae (). They are sometimes called crawling seals to distinguish them from th ...
,
sea lions 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. ...
,
fur seals Fur seals are any of nine species of pinnipeds belonging to the subfamily Arctocephalinae in the family '' Otariidae''. They are much more closely related to sea lions than true seals, and share with them external ears (pinnae), relatively lon ...
and
walruses The walrus (''Odobenus rosmarus'') is a large flippered marine mammal with a discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. The walrus is the only living species in the fami ...
) temporarily leaving the water. Hauling-out typically occurs between periods of
foraging Foraging is searching for wild food resources. It affects an animal's Fitness (biology), fitness because it plays an important role in an animal's ability to survive and reproduce. Optimal foraging theory, Foraging theory is a branch of behaviora ...
activity. Rather than remain in the water, pinnipeds haul-out onto land or sea-ice for reasons such as
reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...
and rest. Hauling-out is necessary in seals for mating (with the exception of the
Baikal seal The Baikal seal, Lake Baikal seal or (''Pusa sibirica''), is a species of earless seal endemic to Lake Baikal in Siberia, Russia. Like the Caspian seal, it is related to the Arctic ringed seal. The Baikal seal is one of the smallest true seals a ...
) and giving birth (although a distinction is generally made between reproductive aggregations, termed "
rookeries A rookery is a colony of breeding animals, generally gregarious birds. Coming from the nesting habits of rooks, the term is used for corvids and the breeding grounds of colony-forming seabirds, marine mammals (true seals and sea lions), and ev ...
", and non-reproductive aggregations, termed "haul-outs"). Other benefits of hauling-out may include
predator avoidance Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avo ...
,
thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
, social activity,
parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
reduction and rest. There is much variation in haul-out patterns among different seal
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
.Hoelzel, A. Rus. (2002). ''Marine Mammal Biology: An Evolutionary Approach''. Blackwell Publishing. . p. 197. Haul-out sites may be segregated by age and sex within the same species. Many species of pinniped have only a few localized rookeries where they breed, but periodically occupy hundreds of haul-out sites throughout the range. For example, the
Australian fur seal The brown fur seal (''Arctocephalus pusillus''), also known as the Cape fur seal, South African fur seal and Australian fur seal, is a species of fur seal. Description The brown fur seal is the largest and most robust member of the fur seals. ...
s breed on only nine islands in
Bass Strait Bass Strait () is a strait separating the island state of Tasmania from the Australian mainland (more specifically the coast of Victoria, with the exception of the land border across Boundary Islet). The strait provides the most direct waterwa ...
but also occupy up to 50 haul-out sites in south-east Australian waters,Gales, Nick; Gales, Nicholas; Hindell, Mark; & Kirkwood, Roger. (2003). ''Marine Mammals: Fisheries, Tourism and Management Issues''. CSIRO Publishing. . p. 259. and
Steller sea lions The Steller sea lion (''Eumetopias jubatus''), also known as the Steller's sea lion and northern sea lion, is a near-threatened species of sea lion in the northern Pacific. It is the Monotypic taxon, sole member of the genus ''Eumetopias'' and ...
have around 50 rookeries throughout their range, but several hundred haul-out sites. Hauling-out behaviour provides numerous benefits to pinnipeds besides reproduction. This behaviour has been shown to be used for activities such as thermoregulation, predator avoidance,
moulting In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...
,
nursing Nursing is a profession within the health care sector focused on the care of individuals, families, and communities so they may attain, maintain, or recover optimal health and quality of life. Nurses may be differentiated from other health ...
, and resting. Haul-out frequency, duration, and site location (i.e. sea-ice, floating-ice, and terrestrial) are all influenced by physical constraints (i.e. air temperature, wind speed, and time of day) and biological constraints (i.e. moulting, age, and sex). Variations in hauling-out behaviour exist among pinnipeds for reasons such as geographical location.


Examples


Weddell seals

Haul-out sites of
Weddell seal The Weddell seal (''Leptonychotes weddellii'') is a relatively large and abundant true seal with a circumpolar distribution surrounding Antarctica. The Weddell seal was discovered and named in the 1820s during expeditions led by British sealing ...
s are not necessarily geographically distinct from one another and vary due to physical factors (i.e. food availability) and biological factors (i.e. age). Weddell seals are high latitude
Antarctic The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...
inhabitants, allowing them to haul-out onto ice as adults year round for foraging. Similar to other pinnipeds, Weddell seals haul-out for reasons such as feeding, rest, avoidance of predators, and thermoregulation. Seasonal variation has been indicated to influence the haul-out patterns of this species, environmental factors such as air temperature and wind speed trigger a shift from long-duration diurnal haul-outs to short-duration
nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...
patterns. Following moulting season the number of haul-outs performed increases allowing the seals to benefit from the increased air temperature and thus decreasing the energetic cost of growing new hair. The haul-out patterns of female Weddell seal are heavily influenced by the age of their pups. In the first week post
parturition Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...
, haul-out frequency is high and females remain hauled-out for longer periods prior to the pups starting to swim. Haul-out frequency decreases as the pups are
wean Weaning is the process of gradually introducing an infant human or another mammal to what will be its adult diet while withdrawing the supply of its mother's milk. The process takes place only in mammals, as only mammals produce milk. The infan ...
ed and mating begins.


Walruses

Walrus The walrus (''Odobenus rosmarus'') is a large pinniped, flippered marine mammal with a discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. The walrus is the only living species in ...
es tend to occupy both terrestrial and sea ice haul-out sites, alternating between the two depending on resource availability. Walruses haul-out onto land primarily for birthing, moulting, nursing, and resting, meanwhile using sea-ice haul-out sites for foraging and predator avoidance. These physiological factors are correlated with both the duration and frequency of haul-outs among walruses. Sea ice sites are more commonly used for shorter and more frequent haul-outs compared to terrestrial sites, which are commonly used to fulfill more time-consuming requirements (i.e. breeding and birthing). Hauling-out is also used as a method of thermoregulation, therefore it is influenced by various environmental factors such as wind speed, temperature, and even time of day. Accounting for these environmental factors, walruses more frequently haul-out from late morning to early evening and avoid hauling-out during weather periods of intense cold or high winds. Haul-out frequency is at a
maximum In mathematical analysis, the maxima and minima (the respective plurals of maximum and minimum) of a function, known collectively as extrema (the plural of extremum), are the largest and smallest value of the function, either within a given ran ...
for walruses during the summer using terrestrial haul-out sites as sea ice sites are then further from foraging grounds. As female walruses haul-out for parturition, the males are
territorial A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or a ...
of the haul-out site surrounding the female
herd A herd is a social group of certain animals of the same species, either wild or domestic. The form of collective animal behavior associated with this is called ''herding''. These animals are known as gregarious animals. The term ''herd'' is ...
. In these instances, hauling-out provides an opportunity for more
aggressive Aggression is overt or covert, often harmful, social interaction with the intention of inflicting damage or other harm upon another individual; although it can be channeled into creative and practical outlets for some. It may occur either reacti ...
and territorial males to mate.


Ringed seal

Ringed seal The ringed seal (''Pusa hispida'') is an earless seal inhabiting the Arctic and sub-Arctic regions. The ringed seal is a relatively small seal, rarely greater than 1.5 m in length, with a distinctive patterning of dark spots surrounded by light g ...
hauling-out occurs throughout any point in the year, however it reaches a maximum during the spring. In comparison to other pinniped species, ringed seals haul-out with a shorter duration year round. Ringed seals have a
diel Diel vertical migration (DVM), also known as diurnal vertical migration, is a pattern of movement used by some organisms, such as copepods, living in the ocean and in lakes. The word ''diel'' comes from the Latin ''dies'' day, and means a 24-h ...
haul-out pattern in which they spend more time hauled-out during the night, an uncommon feature among
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the walru ...
s. Hauling-out spikes an increase in the herding behaviour of ringed seals, particularly in the Ladoga subspecies. Subspecies of the ringed seal prefer different haul-out sites depending on their geographical location and environmental constraints. For example, 5 subspecies of ringed seals prefer hauling-out onto land-fast ice, however ''Phoca hispida ochotensis'' prefers drifting pack ice, meanwhile ''Phoca hispida hispida'' occupies both land-fast ice and far offshore areas of relatively stable ice. The majority of ringed seals however use terrestrial haul-out sites to create birth layers in the snow for newborn seal pups.


Harbour seal

Harbour seal The harbor (or harbour) seal (''Phoca vitulina''), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped (walruses, eared sea ...
s are the most abundant pinniped in the eastern
North Pacific Ocean North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north'' is ...
. Much like other pinnipeds, harbour seals haul-out for reasons such as thermoregulation, breeding, mating, moulting, resting, and foraging. They commonly haul-out onto
intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of Marine habitat, habitats with var ...
ledges,
mudflat Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal fl ...
s,
beaches A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells ...
, and ice floes year round. Haul-out sites are often revisited on a regular basis by the same herd and are heavily affected by tide height. Harbour seals are likely to move haul-out sites in response to inclement weather conditions (i.e. wind chill and wave size) to more favourable sites in rocky reefs, mudflats, and beaches that are exposed during lower tides. Frequency and duration of the behaviour is at a maxima during early afternoon when lower tides and higher air temperatures are prevalent. During parturition and weaning, females spend more time hauled-out ashore until their pups begin to swim, meanwhile males spend less time hauled-out and maintain aquatic
territories A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or an ...
instead. Moulting and predation risk also increase the time spent hauled-out. Despite the increased time ashore for females and decreased time ashore or males during birthing and weaning, biological constraints such as age and sex have not been shown to effect harbour seal haul-outs. Both male and female harbour seals of all ages are consistent with time spent hauled-out. Harbour seals commonly inhabit regions susceptible to human
disturbance Disturbance and its variants may refer to: Math and science * Disturbance (ecology), a temporary change in average environmental conditions that causes a pronounced change in an ecosystem * Disturbance (geology), linear zone of faults and folds ...
s (i.e. industries such as the
fishery Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...
), a factor that has been studied and shown to alter haul-out patterns. Human disturbances negatively influence the duration and frequency of harbour seal haul-outs, decreasing the occurrence of this behaviour as human interference increases.


References

{{reflist Pinnipeds Ethology