Many of the prey species consumed by the resident population display little spatial or temporal variation compared with prey consumed by nomadic
populations. Temporal differences were observed in the diet with the main prey species (house mouse) declining from 88.9% in summer to 66.7% in winter and 40.0% in spring (P<0.01). Conversely, bird and rat consumption increased across the three seasons (16.3, 28.6 and 34.0% for birds, P=0.08; and 15.0, 33.3 and 75.0% for rats, P<0.01; for summer, winter and spring, respectively). Trapping resulted in the capture of house mouse Mus domesticus only, which declined significantly from the first half to the second Selleck ZD1839 half of the year (P<0.01). These data indicate that the eastern grass owl in the coastal zone is a specialist predator of small rodents, but will broaden its diet to feed opportunistically on a range of other species when the preferred prey are less abundant. We conclude that
the capacity to switch between specialized and opportunistic predation, combined with prey that are spatially and temporally more predictable, facilitates shifts between nomadism and residency in the eastern grass see more owl. “
“Alternative morphotypes can confer important selective advantages in different habitats, whereas they can be penalized in other circumstances. In ectotherms, such as reptiles, the body colour can have direct effects on numerous aspects of their existence, such as thermoregulation or prey–predator interactions. Darker melanic individuals show lower skin reflectance and consequently heat up more rapidly and maintain optimal body temperatures more easily than lighter coloured individuals. As a consequence, melanistic individuals of diurnal species in cool areas may exhibit higher body condition, growth rate,
survival and fecundity than lighter coloured individuals. Such advantages of dark coloration may be counterbalanced by a lower crypsis to predators next and a decreased foraging efficiency. We investigated, in two montane populations of asp vipers Vipera aspis, the relationship between (1) colour polymorphism and body condition and length and (2) the coloration of individuals and their elevational distribution. We showed significant relationships between (1) the coloration, body condition and sex of individuals; (2) sexes and reproductive state and morph frequency; and (3) colour morphs that were distributed following an elevational gradient. Hence, colour polymorphism plays an important role in the ecology and evolution of the asp viper and is maintained through differential selective pressures. “
“Estimating paternity patterns provides insights into the importance of competing evolutionary forces on mating systems. The number of sires contributing to a female’s offspring is mostly influenced by her relative promiscuity.