Hastings Natural History Reservation

01 Jul, 07 AM - 30 Jul, 05 AM

Project Summary Rocky Mountain mule deer (Odocoileus hemionus hemionus) females defend fawns that are not their own offspring including fawns from another species. Apparent altruism such as this is hard to explain, because the helper increases its own risk of predation or injury without obtaining an obvious benefit. Most investigations of altruism have focused on adaptive explanations. However, mechanisms underlying behaviour, such as the ability to distinguish individuals seeking help, can result in behaviour that is imperfectly adapted to the environment. For example, the ability of a female to defend her own fawn may depend on her motivation to respond whenever she hears a fawn in distress, even if it bears the cost of defending fawns that are not her own. The altruistic behaviour observed in mule deer might simply be one of a suite of traits correlated with a female?s motivation to defend her own fawn. The presence of such altruism in mule deer is particularly interesting, given that females from a closely related species, white-tailed deer (Odocoileus virginianus), restrict defence to their own offspring. I will conduct a series of playback experiments to test the idea that the defence of non-offspring is associated with a rigid tendency to defend against predators whenever fawn distress calls are heard. Playback experiments will be conducted with genetically distinct populations of deer to determine whether one suite of behavioural traits is associated with an altruistic response (i.e., defense of non-offspring) and another suite of traits with a selective response (i.e., restrict defence to their own offspring). For example, altruistic females, operationally defined as those willing to approach a speaker when hearing distress calls even though they can see their own fawn is safe, would be expected to confront the speaker aggressively and to respond when hearing a second round of calls (i.e., they would not habituate to the calls). Selective females, those that only approach the speaker when they cannot see their own offspring, should not exhibit these traits. If the evolutionary foundation for this behaviour is rooted in maternal care, males would not be expected to respond to distress calls; this is the case with white-tailed and mule deer, but deserves attention with other taxonomic groups. The focus of work this summer will be to test the responses of black-tailed deer during the post-parturition season. Black-tailed deer (O. hemionus) are ideal animals with which to conduct this work, because there is a clade of genetically distinct populations or subspecies that extends from California to Alaska. These populations are genetically and morphologically intermediate between white-tailed deer O. virginianus, and mule deer (O. h. hemionus), the groups with which I have previously worked. Research being conducted in summer 2010 will focus on black-tailed deer found north and south of the San Francisco Bay area. This research will improve our understanding of mechanisms influencing prey defences, social behaviour and parental care in animals. Specific methods Playback tests will be conducted primarily with females having fawns that are two to ten weeks in age. A playback trial consists of setting a speaker into a location that is within 200 m of a subject, or in a location to which we expect a subject to move. A field assistant will be hidden within 100 m of the wireless speaker (e.g., behind a hill or in a ditch) where he or she can use an iPod to turn the speaker on and off. The playback sequence is played for 60 sec, and contains about 12 s of vocalizations. An observer, sitting about 1000 m away with a spotting scope and binoculars, records the subject?s response on audiotape, while a second observer uses a video camera to record the subject?s response. Data are transcribed to paper immediately following the trial. Four types of trials will be run, although the first two will be concurrent: (1) Fawns present vs. absent. The main goal is to compare the response of females when their fawns are hidden at a bedsite (?absent) with their response at times when their fawns stand next to them (?present?). We will use different individuals for these two types of trials, because we cannot control the situation well enough to test the same female on two different days. (2) Habituation trials. Another indication of the mule deer?s rigid response is the fact that they do not habituate to these calls: they responded just as strongly to a second series of calls as they did to the first. In contrast, the response of white-tailed deer wanes once they have heard one series of calls. If a female?s fawn remains bedded in the trials described above, we will play the playback sequence for a second time about 5 minutes after conducting the first trial. Females usually appear to have relaxed and resumed normal behaviour, such as eating or resting, within 1-2 minutes of a trial. (3) Males. In white-tailed and mule deer, only females approach the speaker when hearing juvenile calls and only females defend fawns against predators. We will conduct playbacks with males to determine whether a response to fawn calls is strictly a female behaviour in other taxonomic groups. (4) Response outside the reproductive season. We will return to selected locations during fall or winter to test whether an aggressive response to distress calls is shown by females outside the reproductive season or by females that do not have fawns of their own (Prediction 3). Sample size: Based on the level of variability I anticipate seeing this summer, I expect to conduct about 8-10 trials with females with hidden fawns, 15-20 with females having active fawns, and 8 with males for each population. Geographic range and populations: Playback tests with a particular subspecies or population will be distributed over a large geographic area, about 10,000 sq km, to obtain a sample that includes animals from different habitats and to avoid harassing animals in any one location There will usually be at least 500 m separating locations where trials are conducted to avoid testing the same individual twice, unless we are confident that a different individual is present. In summer 2010, we are working with blacktails in Sonoma County, Marin County and Carmel Valley and surrouding area. The deer south of San Francisco belong to a genetically distinct subspecies (O. h. californicus) and we expect to find behavioural differences from the deer occurring north of the Bay area.

Visit #21799 @Hastings Natural History Reservation

Approved

Under Project # 21913 | Research

Evolution of cooperative antipredator defence: a study using playback tests with black-tailed deer and other ungulates

faculty - University of Winnipeg

Reservation Members(s)

Group of 3 Research Assistant (non-student/faculty/postdoc) Jul 1 - 30, 2010 (30 days)
Susan Lingle Jul 1 - 30, 2010 (30 days)

Reserve Resources(s) | Create Invoice

Bunk House Cottage 4 Jul 1 - 30, 2010