In one striking example, group size increased from a single pair in 2004 to a group of seven in 2005 while territory size declined by almost two-thirds (Fig. 1). Notably, this pair failed to breed in 2005. It is plausible that maintaining a larger territory confers benefits for reproductive success by increasing the distance between offspring and neighbouring conspecifics and reducing infanticide risk. This could outweigh costs of defending a larger area by pairs with offspring. Advantages of maintaining congruent territories may also accrue through elimination of interstitial
areas between groups which can serve as a settling point for dispersing or itinerant individuals which may then seek to expand these small areas and establish AZD2281 concentration their own territory at the expense of resident territory holders (Baker et al., 2000). One would expect that as breeding pairs become more dispersed, a point would be reached where costs of defending additional vacant areas outweigh any benefits and render an expansionist strategy untenable. PI3K inhibitor Black-backed jackal social organization varied with 43% of dominant pairs accompanied by one to six subordinates. Group size increased, and subordinates were more likely to be present, further from the colony. During the denning period, jackals face challenging trade-offs between the need to nurse, provision and protect offspring at the den and food acquisition
and territory defence away from the den. Having additional group members that contribute towards offspring care (e.g. provisioning) may help offset this trade-off for breeders living further from the colony while subordinates gain direct and indirect benefits through group living and helping (Jennions & Macdonald, 1994). An alternative, not mutually exclusive, explanation is that variation in territory size, population density
and within-territory density influences dispersal behaviour of subordinates. During mating subordinates may be excluded from their natal territory (Loveridge & Nel, 2004). Whether subordinates ‘float’ in territory MCE公司 edges or disperse will depend on the balance of costs and benefits. Close to the colony, where territories are small, population density and within-territory density are high and there is high intraspecific competition for space, dispersal may be the favoured strategy. In contrast, further from the colony where territories are large and density is low, jackals may adopt a ‘floating’ strategy and later return to their natal (or other) group, assuming the benefits of not dispersing outweigh the costs. Commuting systems have been described in other social carnivores reliant on clumped and unpredictable food resources (Hofer & East, 1993b; Höner et al., 2005). However, there are no records of jackals operating a commuting system elsewhere in their range, highlighting the flexibility of this adaptive species.