Evidence Of Individual Specialization Research Articles

Isotopic evidence of individual specialization toward free-ranging chickens in a rural population of red foxes

Abundance and distribution of food resources directly influence adaptative foraging strategies, which are strongly related to individual fitness and population demography. Specialization toward food resources is commonly observed in predator species, both at population and individual levels. When predation of livestock occurs, human-wildlife conflicts rise and livestock producers require efficient management of predators. In the Bresse region (eastern France), free-ranging poultry farms annually suffer from losses due to predation of chickens by several bird and mammal species, including red foxes (Vulpes vulpes). We quantified the diet of several red foxes in this region and investigated dietary specialization on chicken using stable isotope analysis. Vibrissae (i.e. whiskers) of 68 wild foxes sampled throughout the year were cut into fragments to measure inter- and intra-individual variability of diet, allowing us to reconstruct the diet of individual foxes on an average of 134 days. At the population level, over 70% of the diet was composed of rodents and chickens. Within the population, we found contrasting carbon isotopic signatures, indicating that some foxes preferentially consumed prey with high δ13C values, likely corresponding to Bresse chickens fed with maize, while others consumed wild food resources. We estimated that 4.4% (i.e. 3/68 foxes) of the fox population was composed of individuals that specialized in predating chicken. Chicken predation was higher in females than males and occurred more often in summer, when females were rearing kits. The availability of an easily catchable food resource could explain why some red foxes included chickens in their diet. These results call for management actions focused on specialized foxes.

No task specialization among helpers in Damaraland mole-rats

The specialization of individuals in specific behavioural tasks is often attributed either to irreversible differences in development, which generate functionally divergent cooperative phenotypes, or to age-related changes in the relative frequency with which individuals perform different cooperative activities; both of which are common in many insect caste systems. However, contrasts in cooperative behaviour can take other forms and, to date, few studies of cooperative behaviour in vertebrates have explored the effects of age, adult phenotype and early development on individual differences in cooperative behaviour in sufficient detail to discriminate between these alternatives. Here, we used multinomial models to quantify the extent of behavioural specialization within nonreproductive Damaraland mole-rats, Fukomys damarensis, at different ages. We showed that, although there were large differences between individuals in their contribution to cooperative activities, there was no evidence of individual specialization in cooperative activities that resembled the differences found in insect societies with distinct castes where individual contributions to different activities are negatively related to each other. Instead, individual differences in helping behaviour appeared to be the result of age-related changes in the extent to which individuals committed to all forms of helping. A similar pattern is observed in cooperatively breeding meerkats, Suricata suricatta, and there is no unequivocal evidence of caste differentiation in any cooperative vertebrate. The multinomial models we employed offer a powerful heuristic tool to explore task specialization and developmental divergence across social taxa and provide an analytical approach that may be useful in exploring the distribution of different forms of helping behaviour in other cooperative species.