Tim P. Jackson

Solutions for elephant Loxodonta africana crop raiding in northern Botswana: moving away from symptomatic approaches

Conflict between people and elephants in Africa is widespread yet many solutions target the symptoms, rather than the underlying causes, of this conflict. To manage this conflict better the underlying causes of the problem need to be examined. Here we examine factors underlying spatial use by elephants and people along the Okavango Panhandle in Ngamiland, northern Botswana, to provide ways to address the causes of the conflict between elephants and people. We found that (1) elephant spatial use was a function of season, (2) spatial use did not differ between breeding herds and bull groups, (3) spatial use by elephants and people only overlapped significantly at night, during the dry season, (4) crop raiding by elephants was a function of season and social grouping, and (5) crop raiding by elephants had social and economic implications. Based on these results we suggest measures to manipulate elephant spatial use to reduce the causes of this conflict. We also reflect on present compensation measures for elephant crop damage and advocate that a more direct performance payment approach may benefit both the Botswana Government and local farmers.

Food, reproduction and survival in mice on sub-Antarctic Marion Island

The house mouse Mus musculus is the most widespread introduced mammal on sub-Antarctic islands, where it may alter ecosystem function. Ambient temperature and food availability affect reproduction and survival for mice. It is unclear how these factors influence mouse demography in the sub-Antarctic, and we tested the influence of food experimentally on Marion Island. Using food supplementation trials, we did not alter reproduction or overwinter survival. Alternatively, we argue ongoing climatic change on Marion could increase mouse densities through summer, while increased winter survival may reduce population growth rates the following summer through density dependence. The overall influence of these apposing forces depends on their relative strengths but may limit changes in mouse numbers with ongoing changes in climate in the sub-Antarctic.

Are Cape Ground Squirrels (Xerus inauris) Induced or Spontaneous Ovulators

Abstract Little is known about the ovulation patterns in ground squirrels, even though the timing of ovulation could influence mate-order effects and sperm competition, which have been documented in a number of species. The Cape ground squirrel (Xerus inauris) is a social, nonhibernating, semifossorial rodent with aseasonal reproduction. Evidence suggests that sperm competition is an important aspect of male reproductive success in this species. We examined whether the Cape ground squirrel is an induced or spontaneous ovulator. Fifteen reproductive adult females were removed from natal colonies and housed individually. Females were subjected to 1 of 3 trials: no male contact, chemical and visual contact but no physical contact with intact males, or direct contact with epididymectomized males. Females from each of the 3 experimental treatments exhibited similar urinary progesterone metabolite concentrations and qualitative ovarian histology. Neither the presence of males nor copulation appear necessary for ovulation to occur, and ovulation in this social African ground squirrel appears to be spontaneous.

Sex- and Species-Specific Growth Patterns in Cryptic African Rodents, Mastomys natalensis and M. coucha

Abstract The sibling multimammate mice, Mastomys natalensis and M. coucha, occur throughout southern Africa, exhibiting limited sympatry. We examine body mass and growth characteristics of both species, from birth to 26 weeks of age. Gompertz growth curves were fitted to data for body mass and lengths of head and body, tail, hind foot, and ear. Males of both species exhibited greater asymptotic values, faster maximum growth rates, later age of maximum growth, and extended growth periods than females. However, neither species established body mass dimorphism before weaning, suggesting that differential maternal investment between sexes is not important in preweaning growth. Furthermore, M. natalensis exhibited significantly faster maximum growth rates to reach a greater predicted asymptotic mass than M. coucha. We discuss these results in relation to mating system and interspecific competition.

THE EFFECT OF CHANGING CALL DURATION AND CALLING BOUTS ON VIGILANCE IN BRANTS' WHISTLING RAT, PAROTOMYS BRANTSII

Summary The function of variation in single call duration and alarm calling bouts was investigated in Brants’ whistling rat, Parotomys brantsii, by means of playback experiments and video analyses of the vigilance displayed. Short calls are produced in high-risk situations, and long calls in low-risk encounters, but these calls apparently do not communicate this variance in risk to conspecie cs. Both short and long single calls induced heightened vigilance in receivers, but rats did not respond differentially to the two call types, and it was concluded that P. brantsii alarm calls are not functionally referential. Multiple calls maintained a state of increased alertness in receivers for a longer period than single calls, even after the bouts had ended, but long bouts (duration: 64 s) did not lead to longer periods of vigilance than short bouts (29 s). Thus the tonic communication hypothesis is only partially supported by our study.