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Many mammals use the change in day length to time physiological and behavioural activities on a seasonal basis. Particularly, mammals from temperate regions use photoperiod to regulate reproductive functions; however, information on the role of photoperiod in small mammals from the tropics and subtropics is scarce. We studied the response of the reproductive system of male eastern rock sengis ( Elephantulus myurus Thomas and Schwann, 1906) from southern Africa to photoperiods of differing length. Elephantulus myurus breeds seasonally during the spring and summer months of the southern hemisphere despite its subtropical distribution. It is one of only three sengi species known to breed seasonally. Fourteen male E. myurus were subjected to either long-day (LD; 16 h light (L) : 8 h dark (D)) or short-day (SD; 8 h L : 16 h D) photoperiods and the photoperiodic effects on the testes, testosterone concentration, and body mass were examined. Testicular volume and mass, seminiferous tubule diameter, and body mass were not significantly different between LD and SD conditions. However, plasma testosterone concentration was significantly lower in males on LD photoperiods compared with SD photoperiods. Male E. myurus may not use photoperiod as a cue to control seasonal reproductive changes. Other environmental factors such as temperature, rainfall, food abundance, or social factors are possibly influencing seasonal reproduction in this species. [ABSTRACT FROM AUTHOR]

Because environmental conditions vary seasonally in most regions, many small mammals reproduce at a specific time of the year to maximize their reproductive success. In the tropics and subtropics, the breeding season is usually determined by the extent of the dry and rainy seasons. We investigated the seasonality of reproduction in the eastern rock elephant-shrew ( Elephantulus myurus), over a 12-month period and attempted to elucidate the factors that may influence seasonal reproduction in this endemic African mammal. E. myurus breeds seasonally during the warm and wet spring and summer months and cessation of breeding occurs during the cold and dry winter months of the southern hemisphere. Pregnant females were only collected from August through to January. Ovarian size and plasma progesterone started to increase a few months prior to the first rains, were highest in October and decreased thereafter. Follicular growth and corpora body numbers corresponded to this seasonal reproductive pattern. Testes and seminiferous tubule size and plasma testosterone concentration has already started to increase during the coldest months, 2 months prior to reproductive onset in females. We propose that seasonal reproduction evolved in E. myurus because of seasonally changing food availability brought about by severe seasonal changes in rainfall and ambient temperature. The direct effects of rainfall and ambient temperature on reproduction of E. myurus are ambiguous, and we discuss other environmental factors that may trigger reproductive onset in this species. [ABSTRACT FROM AUTHOR]

Ticks are important vectors of pathogens of medical and veterinary importance worldwide. In spite of their economic importance, our current knowledge about the factors affecting tick prevalence and abundance in tropical and subtropical regions is rather limited. Both abiotic (e.g. temperature) as well as biotic variables (e.g. host sex) have been identified as key determinants of distributions. Eastern rock sengis or elephant shrews ( Elephantulus myurus, Macroscelidea: Cacroscelididae, Thomas & Schwann) are widely distributed throughout Africa and can harbour a large number of tick species and substantial tick burdens. In the present study, we evaluated the contribution of climate and host factors on tick burdens of sengis. Throughout the year sengis carried high abundances of immature stages of a single tick species, Rhipicephalus sp. near warburtoni. There was no evidence that host parameters affected tick burdens. However, larval abundance decreased with increasing ambient temperatures and both larvae and nymphs were negatively affected by rainfall 2 months before the sampling month. In addition, nymphal burdens decreased with increasing minimum temperatures. Our results suggest that climate factors are the largest constraint for the immature stages of R. sp. near warburtoni and that eastern rock sengis could play a crucial role in the dynamics of tick-borne diseases as a result of the large tick burdens they can sustain. [ABSTRACT FROM AUTHOR]