Peter J. Stephenson

Reproductive Energetics of the Tenrecidae (Mammalia: Insectivora). I. The Large-Eared Tenrec, Geogale aurita

Body mass, body temperature (Tb), and oxygen consumption were measured in male and female large-eared tenrecs (Geogale aurita) during the breeding season. Body temperature paralleled ambient temperature (Ta) in all individuals, though Tb was more elevated above Ta in pregnancy and lactation, especially if these events occurred concurrently. Resting metabolic rate (RMR) in nonreproducing adults at 30°C was 7. 73 mL O2 · h−1 (53% of the value expected from body mass). It did not significantly increase with body mass, except in some pregnant individuals (or those concurrently pregnant and lactating). Resting metabolic rate increased during reproduction and reached peak levels during gestation. The energy cost of gestation with simultaneous lactation was not additive and represents an energy saving. Resting metabolic rate in pregnancy and lactation was not influenced by litter size, and this implies there is no fixed minimum energy requirement for reproduction in this species. Mean daily energy expenditure of nonreproducing G. aurita was 9.67 kJ · d−1 (2.6 × RMR). Daily energy expenditure during gestation attained higher levels than those attained in nonreproducing individuals and gradually decreased during lactation. It is proposed that an increased level of RMR may be essential for reproduction in G. aurita. However, the cost of reproduction is often reduced by conception at postpartum estrus and concurrent pregnancy and lactation.

RESTING METABOLIC RATE AND REPRODUCTION IN THE INSECTIVORA

Abstract This paper investigates the relationship between body mass, resting metabolic rate (RMR) and life history in the insectivore families Tenrecidae and Soricidae. RMR and a number of life history variables scale to body mass within both families. Residuals from least squares regression analysis produced relative or mass-independent values which were used to determine the relationship between RMR and reproduction. Within the Tenrecidae, RMR was not correlated with any of eight reproductive variables when the effect of mass was removed. The failure of species in this family to gain a reproductive advantage from elevated RMR may be due to phylogenetic constraints on reproduction. Species with elevated RMR may benefit from improved homeothermy rather than increased reproductive output. In the Soricidae, an increase in relative RMR was associated with a decrease in gestation length, an increase in specific foetal growth velocity and an increase in liter size. The possiblity that energetic and reproductive strategies in the Soricidae may have evolved under separate constraints is discussed. It is condluded that RMR is sometimes associated with life histories in the Insectivora, but its effect varies significantly between families.

Conservation of mammalian species diversity in ambohitantely special reserve, Madagascar

Abstract Ambohitantely Special Reserve protects one of the few remaining remnants of native forest on the Central Plateau of Madagascar, yet its fauna is poorly studied. This paper describes the first systematic small mammal trapping programme to be implemented in the reserve. Between August 1988 and March 1990, Sherman and pitfall traps revealed the presence of four endemic tenrec species and an introduced rat. Diurnal and nocturnal surveys recorded three lemur species. The terrestrial mammal community of Ambohitantely is compated with other reserves in Madagascar. It is concluded that the reserve has a relatively species-poor mammal fauna which may be due to its isolation from contaguous forest blocks. It is postulated that the continued presence of wild boar and domestic cattle in the reserve and regular burning of the surrounding savannah have a detrimental effect on the native fauna and flora. The consequences for conservation are discussed.

Field metabolic rate in two species of shrew-tenrec, Microgale dobsoni and M. talazaci

Abstract Doubly labelled water (DLW) was used to determine field metabolic rate (FMR) in the shrew-tenrecs Microgale dobsoni and M. talazaci. Measures were obtained on six animals in their natural habitat and on five individuals in captivity. Mean FMR for nonreproducing M. dobsoni (mean body mass 42.6 ± 1.7 g) was 77.1 ± 3.2 kJ/d (CV = 53.7%, N = 4), 3.8 times resting metabolic rate (RMR). Mean FMR for nonreproducing M. talazaci (mean body mass 42.8 ± 4.9 g) was 66.5 ± 14.1 kJ/d (CV = 51.9%, N = 6), 3.2 times RMR. FMR within each species was not significantly correlated with body mass. This may in part reflect the large variation among individuals combined with the small sample size. FMR in shrew-tenrecs was within the range of FMR found in similar sized rodents, although variation was greater in the tenrecs. The high variability of FMR within the Tenrecidae may be a result of variations in body temperature. FMR/RMR ratios for both species fell within the range determined for other small mammals. The present study therefore offers further evidence to support a relationship between FMR and RMR.