Harbour seals throughout their range are known to "haul out" onto land according to a daily cycle, which has never been fully investigated. This cycle may represent a tradeoff between the need to forage and the need to avoid aquatic predators; if so, seals should forage when prey availability is greatest and remain hauled at other times. A model based upon these premises accounted for approximately two thirds of the variation in observed hauling behaviour at a harbour seal colony in the Strait of Georgia, once other environmental effects had been filtered from the data. Some such effects could not be corrected for; since air temperature and solar radiation follow the same general pattern as that predicted by the hauling model, the possibility that hauling occurs in response to thermal conditions could not be excluded. This issue was addressed by correlating hauling activity at three seal colonies with "flux" Fs, an index of heat exchange between a seal and its environment. Once time of day and tidal effects were accounted for, there was no evidence of a positive correlation between hauling and Fs. However, under warm summer conditions there was a steep negative relationship. This is consistent with the possibility that hauled harbour seals are vulnerable to hyperthermia due to their adaptation to an aquatic lifestyle; the same blubber layer which keeps them warm when immersed may make it difficult for them to lose excess heat when on land. This was confirmed by a series of controlled experiments. Captive seals overheated when exposed to a radiant thermal environment similar to that in which wild animals stopped hauling. These data allowed me to derive an equation which described the rate of change in a seal's core temperature as a function of both present core temperature and Fs. I incorporated this function into a simulation model which described hauling behaviour in terms of a foraging/predator-avoidance tradeoff. The model performed well when used to predict the haul out durations of a sample of wild radio-tagged harbour seals in a known thermal environment. However, it is apparent that the processes which constrain hauling in this species are somewhat better understood than those which presumably cause it. An understanding of the foraging efficiency of harbour seals throughout the day, and of the predation risks they face, is probably fundamental to an understanding of hauling; yet these issues remain virtually unexplored. / Science, Faculty of / Zoology, Department of / Graduate

The behavioral responses of lynx (Lynx canadensis) to declines in snowshoe hare (Lepus americanus) abundance were examined in the southwestern Yukon. Between April 1982 and June 1984 11 lynx were radio-tagged and monitored within and near the Kluane Game Sanctuary. Lynx mean home range size increased from 13.2 to 39.2 km² concurrent with a decline in snowshoe hare abundance from 14.7 to 0.2 hares/ha. Below about 0.5 hares/ha several lynx abandoned their home ranges and became nomadic, although they remained within the general study area. Track transects through areas known to have different snowshoe hare densities indicated that, lynx concentrated their foraging efforts in areas of relatively high snowshoe hare abundance. Lynx abandoned these areas after hare abundance declined. Lynx foraging effort in terms of distance travelled per day showed a curvilinear relationship to snowshoe hare abundance. Straight-line daily travel distance remained constant at 2.2 to 2.7 km/day above 1.0 hare/ha. Below 1.0 hares/ha, straight-line daily travel distances increased rapidly, reaching 5.5 km/day at 0.2 hares/ha. Three of 7 radio-tagged lynx dispersed 250 km or more from the study area during the period of rapid decline in hare abundance in 1982. No similar long distance dispersal was recorded after hare densities stabilized at less than 1.0 hares/ha. Trapping mortality was responsible for the loss of 7 of 9 radio-tagged lynx that travelled outside the game sanctuary. One lynx died, and is believed to have starved, during the winter or spring of 1984. The high rate of trapping mortality outside the game sanctuary suggests that refugia in wilderness areas are important in maintaining lynx populations during periods of low recruitment. / Science, Faculty of / Zoology, Department of / Graduate

One schedule of reinforcement that is used to decrease the rate of a target behavior is differential reinforcement of low rates (DRL). During this schedule, reinforcement is delivered for a target response if it occurs after a certain amount of time has passed since the last instance of this target response. The current study used a table-top game called PORTL and college student participants to investigate how collateral patterns develop and are disrupted during DRL schedules. After the participant developed a collateral pattern of behaviors with the objects, the researcher removed one of the objects that was part of the pattern and waited for a new pattern of behaviors to develop. Once the participant developed a new collateral pattern, the researcher removed a second object. This continued until there was only one object present. Results showed that the rate of reinforcement decreased following the removal of each object, then slowly increased as a new pattern developed.

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