COMPARISON OF BEHAVIORS IN CAPTIVE AND WILD POLAR BEARS

CHARACTERISTICS OF WILD POLAR BEARS:

 HABITAT:

            Ice – The preferred habitat of the polar bear is the annual ice that forms next to the shorelines of the continents and archipelagos throughout the circumpolar Arctic.          Polar bears prefer sea ice habitat with leads  (water channels through ice which may remain ice-free for only a few minutes to several months, depending upon weather conditions and water currents.)  This is where they seals, using  sea ice as platform.  They also utilize polynyas  (areas of open surrounded by ice that remain open throughout the year due to winds, upwellings, and tidal currents) which are important breathing and feeding areas for wintering or migrating marine mammals and birds, making them ideal hunting grounds for the bears.

LAND – Some polar bears spend part of the year on land.  Bears from warmer climates may become stranded on land.  In summer, sea ice melts along the coastlines, and pack ice  (floating sea ice or floes, not connected to land) moves north.  Most pregnant females spend the autumn and winter in maternity dens.

 

LONGEVITY – Polar bears are capable of living 20 – 30 years but only a small percentage of them live past 18.  At the top of the food chain, adult polar bears have no predators; mortality is mostly due to the hazards of the harsh Arctic environment.  However, males occasionally kill other male competing for mates, and will also periodically kill females protecting cubs.  Cubs less than one year old sometimes are prey to adult male polar bears and other carnivores such as wolves.  Malnourished mothers may also cannibalize newborn cubs.

 

HUNTING

Polar bears must spend at least half their time hunting because usually less than 2% of their attempts at catching prey are successful.  Even during the spring and early summer, when seals are most abundant and accessible, a bear catches only every four or five days.

 

HUNTING METHODS

            Still Hunting – still-hunting is the most common method of hunting year-round.  The polar bear remains motionless beside a breathing hole or lead edge waiting for a seal to surface.  When it does, the polar bear bites the head or upper body, and then flips the entire seal onto the ice.  Still-hunting usually takes less than one hour, but polar bears will wait much longer if necessary.

            Stalking on Land and Aquatic Stalking – this method is used in summer when seals haul out on sea ice.  Once spotted, the seal is slowly and steadily stalked by the polar bear.  At 50 feet away it will suddenly charge.  With its claws pr teeth the polar bear grabs the seal before it can leave the ice.  Polar bears sometimes swim underwater to stalk distant seals lying at the edge of an ice floe.  When they hunt in this manner they appear to memorize the route to the seal before slipping quietly into the water.  As the bear nears the seal it stealthily pokes the tip of its nose out to breathe, silently slips backward until it is submerged, and then swims rapidly underwater until it needs to breathe again.

Stalking birth lairs – stalking ringed seals at their birth lairs is a hunting method polar bears use in spring when ringed seals give birth tot heir pups.  This method is used most commonly by polar bear females with cubs less than one year old, for several reasons: mother seals and pups have the high fat content needed for hungry polar bear mothers and their growing cubs, male polar bears that may attack young polar bear cubs don’t normally hunt seals in birth lairs, and the lairs are usually on sea ice attached to land, allowing young cubs (who have little protective blubber) to avoid crossing water. 

Daily activity cycle

Polar bears are most active the first third of the day and least active the final third of the day. . In the Canadian Arctic, adult female polar bears with cubs hunt about 19% of their time during the spring and about 38% of their time during the summer. Adult male polar bears hunt about 25% of their time during the spring and about 40% of their time during the summer (Stirling, 1978).

When not hunting, polar bears are often sleeping or resting. a.) On warm days polar bears sprawl out on the ground or ice, sometimes on their backs with their feet in the air. They may also make temporary snow or earthen pits to lie in. b.) On cold days polar bears curl up and often cover their muzzle area. During the winter, some polar bears excavate temporary dens or find natural shelters to stay warm. They may use these shelters for several months at a time.

SOCIAL STRUCTURE

Polar bears are basically solitary. Usually, only two social units exist: (1) adult females with cubs, and (2) breeding pairs. That said, polar bears will aggregate (gather in groups) under several conditions: (1) to feed on large whale carcasses and at dump sites, (2) in some southern regions, like Hudson Bay, bears aggregate on land during the ice-free summer and autumn months, and (3) occasionally adult and sub adult (in the case of polar bears this refers to ages 2½- 5 or 6 years) males will feed and travel together for short periods of time.

Social behavior

Breeding pairs remain together for one week or more, mating several times. The most constant social interaction occurs between mother and cubs. Polar bear mothers are attentive, frequently touching and grooming their cubs. Cubs remain with their mothers for 2½years, partly because they need protection from other bears, but also because they need to be taught how to hunt. The cubs follow their mothers on the sea ice throughout the year and watch her hunt in all kinds of conditions, and then they practice hunting themselves. This learning is critical to their eventual survival. The hardest period of a polar bear's life is the first year of independence when it can no longer rely on sharing the seals that have been killed by its mother. Point Defiance's three younger bears, Blizzard, Glacier and Nanuyaaq, all found themselves reliant on human care before this critical training period could take place, making them non-releasable.

 

Aggression

Aggression occurs between males during the breeding season, and when males attempt to steal food caught by other polar bears. During the late fall, levels of testosterone (the male hormone) are lower than at any other time of year, so males fasting along the coast of Hudson Bay, waiting for freeze-up, show little aggression toward each other. Nevertheless, males of similar size still undertake extended ritualized fights to hone their motor skills for when they will need them.

 

Play

Polar bears sometimes like to play. Except during periods of very cold weather, bears of all ages enjoy swimming, especially cubs and sub-adults. As they walk across the ice, young bears may run towards the water and "belly flop" into it with a huge splash. They will also pound the ice with their feet in order to break it. Young cubs chase and tackle their siblings. While with their mother, and trying repeatedly to copy her behavior, cubs become bored from time to time and begin playing, but play itself can be extremely important as it helps cubs develop some of the motor skills they will need in order to survive as adults. Play fighting has also been observed between aggregating sub-adult and adult male polar bears.

CHARACTERISTICS OF CAPTIVE POLAR BEARS

Habitat and Environment

Generally speaking, animals housed in a barren environment show an overall decrease in interaction with the environment. This comes to expression in a variety of symptoms (Wemelsfelder, 1990). The animals lie down and sleep more, and spend significantly more time sitting. On the other hand, they over- react to novel and/or unexpected events with fearful and aggressive responses. Furthermore, the animals may develop stereotyped patterns of behavior. Such patterns consist of high repetitive and uniform sequences of behavior, which seem to be of no direct functional value to the animal. Examples are bar-biting, stereotyped pacing, as shown by zoo animals such as polar bears and wolves, and various locomotory stereotypes in laboratory primates. Sometimes such behavior can be damaging to other animals; licking and nibbling tails and ears of offspring may for example induce cannibalism.

Feeding

Most captive bears are given food directly to them.  They do not hunt for prey which makes them idle.  Because of this, they become bored and stereotyped.  In a study conducted in the United Kingdom, it is said that food presentation has a big impact on the behavior of the polar bears.  Location, presentation, and time of food delivery are important and may also vary.  Occasionally keepers will deposit only the scent of food in an exhibit.  Just as they would in the wild, exhibit animals may spend hours looking for the origin of the food scent.   To enhance randomness and variety where diet is concerned, sometimes food treats or appropriate live items are placed in the exhibit.  One popular enrichment strategy is to place food treats inside a puzzle that the animal must manipulate in order to dispense the food item.  Sometimes, in cases where processed foods are normally fed, exhibit animals may be given un-processed food or even whole carcasses to feed on.  Fur and feathers can be important features for food handling to an animal.  In carnivores, carcass feeding has been shown to promote the health of the teeth, gums, and pallet (Ziegler, 1995). 

            Stress is another factor of concern. It has been suggested that the stress of life in a cage might contribute to the development of abnormal behaviors. The inability of the animal to escape from these experiences might lead to adoption of stereotyped behaviors as a means of coping with an aversive environment. Some studies have indicated that stereotypic behavior produces a 'trance-like' state (Stevenson, 1983) and is linked to reduced awareness of the environment associate stereotypes in human children with analgesia.

Moreover, Wemelsfelder proposes that in long-term captivity, animal behavior gradually loses its active and flexible character. In the development of abnormal behavior such as stereotypes, we see behavior becomes increasingly rigid, and loses its flexibility. The self-directedness of the behavior shows animals close themselves off from their environment, rather than interact with it. One may object and hold that such a process can still be regarded as an adaptation to a barren environment. The non-adaptive character of abnormal behavior comes, however, best to expression in the response to novel stimuli or a novel environment.

POSSIBLE INDICATORS OF DISTRESS IN ANIMALS

Some possible indicators of distress in animals include 1.) Evidence of physical ill health, 2.) Evidence of frequent occupational diseases, 3.) Need for the use of drugs and/or surgery to maintain the system of husbandry and also 4.) Behavioral changes.  Under the fourth category, such include a.) Performance of abnormal behaviors (that are not normally in the animals repertoire and which appear to be of little benefit to the animal: e.g. running at bars, pacing), b.) stereotypes i.e. the performance of repeated behavior fixed in all details and apparently purposeless (e.g. crib-biting, wind-sucking, weaving, head twisting) c.) large differences in time budgets from the wild or feral animal, d.) substantial increases in behavior related to frustration or conflict (e.g. often behavior relating to locomotion and/or cutaneous  stimulation) and e.) substantial ontogenic behavioral changes (animals performing behavior characteristics of a very different time in their development e.g. calves of 16 weeks walking as if they were a day or so old)

The fifth possible indicator is Behavioural restrictions, which is the inability to perform all the behavior in the animals’ natural repertoire, which does not cause severe or prolonged suffering to others.

 

FIGURE 38 BEARS Maintenance behaviour. Number of minutes/bear hour observed.
.	BEARS
Observed hours	65
Number of individuals	9
.
1) Lying	18.0
2) Sleeping	3.8
3) Standing	7.9
4) Eating	3.7
5) Sitting	3.7
6) Moving	10.1
7) Drink	1.2
8) Hind leg (stand)	0.2
9) Defecate and urinate	0.1
10) Abnormal (stereotypes)	0.5
11) Touch other	4.0
12) Human contact	16.8
13) Pacing	18.3

 

FIGURE 39 BEARS Other behaviour Occasions/observed bear hours the named behavioral categories occurred.
.	BEARS
Observed hours	65
Number of individuals	9
.
1) Abnormal	2.3
2) Frustration	2.4
3) Social a) affiliative	11.4
b) aggressive	0
c) vocalise	0.7
4) Object directed	6
5) Self directed	7.2
6) Locomotion a) run	0.03
b) climb	0.38

Abnormal behavior

The bears displayed no obvious signs of neurotic or pathological behavior (Figures 38 and 39). Pacing occurred for 18.3 minutes per hour (30%). This is very high. The bears were not studied in zoos so we have no comparable figures. Other studies suggest that this figure may well be in line with the normal figure for zoo bears.

Stereotypes

Bears are particularly prone to developing stereotypes, particularly in zoos. One circus bear had a stereotypic head twist. This occurred for 0.52 minutes/observed bear hour. No other stereotypes were observed, although the sample was small.

Increase in aggression

The bears showed no aggression either to humans or to other bears during the observational periods.

Time budget changes

The bears were active during the observational periods, spending over 10 minutes in every hour moving around in their small beast wagons. They lay for 18-minutes/animal hour, but only 3.8 minutes were spent sleeping. They also sat, stood on their hind legs, spent time touching each other (4 minutes/animal hour) and much time in human contact (16.8 minutes/animal hour). We have no comparable figures from the wild or zoo animals at present.

Frustration and conflict

Behavior that might be associated with frustration or conflict, such as head shaking, head nodding, running at bars, self-scratching, vocalizing, was relatively common: 2.4 times/bear hour - relatively high compared to some of the other species.

Fear

There was no evidence of fear (fleeing, freezing) recorded in the bears.

Summary of distress displayed in bears

Bears did show some evidence of distress; some stereotypic performance, abnormal pacing and bar biting, relatively high levels of behavior possibly associated with frustration. They were active, perhaps abnormally so, but remarkably unaggressive.

 

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