Multiple causes of sexual segregation in European red deer: enlightenments from varying breeding phenology at high and low latitude

Abstract

Sexual segregation outside the mating season occurs in most species of sexually dimorphic ungulates and has been extensively described in the literature, but the mechanisms causing segregation are still debated. The detailed pattern of sexual segregation throughout the year has rarely been presented for mammals, and no study, to our knowledge, has used latitudinal-related variation in breeding phenology to shed light on the underlying mechanisms. Recent methodological developments have made it possible to quantify separate components of segregation (social, habitat) and activity synchrony in animal groups, but these major improvements have so far been little used. We observed European red deer year round at two widely different latitudes (France and Norway) and tested three different mechanistic hypotheses of segregation related to: (i) predation risk; (ii) body-size-related forage selection; and (iii) activity budget. Habitat segregation peaked during calving in both populations and dropped rapidly after calving. Females with calves were more segregated from males than were females without calves, pointing to a key role of antipredator behaviour even though large predators are absent in France and extremely rare in Norway. However, at both sites individuals also grouped with their own sex within habitat types (i.e. social segregation), and individuals in mixed-sex groups were less synchronized in activity type than individuals in either unisex male or unisex female groups, suggesting that differences in activity budgets are involved. Social segregation peaked during calving and was lowest during the rut (indicating aggregation) in both populations; these activities occurred one month later in the Northern populations, corresponding well with known differences in breeding phenology. We conclude that latitude-dependent breeding phenology shapes the seasonal pattern of sexual segregation and that sexual segregation in ungulates has multiple causes.

Hierarchical path analysis of deer responses to direct and indirect effects of climate in northern forest

“…Part of this is also due to the large quotas and limited time for hunting, which for moose (Alces alces) populations have been shown to reduce selectivity (Solberg et al 2000). It is simply a high cost in terms of lost chances to be selective in the forested habitat along the west coast of Norway, where group size of red deer is small (average of 1.5 female per male in mixed groups; Bonenfant et al 2004). The only probable bias we may have (though not documented) is that females with offspring are less likely to be shot than females without (as reported for Norwegian moose populations; Nilsen & Solberg 2006).…”

Does the Jarman–Bell principle at intra-specific level explain sexual segregation in polygynous ungulates? Sex differences in forage digestibility in Soay sheep

“…The Jarman-Bell principle was originally formulated using allometric analyses between ungulate species that differed by 3 orders of magnitude in body mass, so it is questionable whether the relationship holds to the intraspecies level (Clutton-Brock and Harvey 1983;Bonenfant et al 2004;Pérez-Barbería et al 2007) and whether sexual dimorphism in body mass in extant ungulates is sufficiently marked to produce any difference in food digestion efficiency (Barboza and Bowyer 2000;Bonenfant et al 2004;Pérez-Barbería et al 2007). …”

A Migratory Northern Ungulate in the Pursuit of Spring: Jumping or Surfing the Green Wave?

“…We found a positive relationship between CIRG and the marking weight for male red deer but not for females. The lack of an effect in females could be explained by the constraints imposed by calves at heel (Bonenfant et al 2004) or if females allocate surplus energy to reproduction (Bronson 1989). We also found indirect support for a possible fitness effect: the proportion of migratory deer in an area increases as the average benefit of migrating (in terms of a gain in springness) grows ( fig.…”