Pine martens experience a “false heat” in late winter in which increased aggressive social behavior forces the dispersal of remaining young before the new litter is born.

Social behavior of the pine marten intensifies in late winter, between February and March, as evidenced by increased scent marking frequency, intersexual tolerance, intrasexual aggression, and hormonal levels. The term “false heat” has been applied to this behavioral enigma.

This was initially thought to be a mating period, but it is clear that mating does not occur until summer. In addition, males have not undergone spermatogenesis yet. This does correspond to implantation and the beginnings of pregnancy, however.

Due to the unexplained occurrence of extra, subadult individuals only in the early winter months, it has been suggested that the aggressive behavior serves to force dispersal of these remaining young from the previous summer before the new litter is born.

Sources: (Clevenger, 1993; Nowak, 1999; Schröepfer, Wiegand, & Hogrefe, 1997; Schwanz, 2000; Zalewski, Jedrzejewski, & Jedrzejewska, 1995)
Image: Thomas Shahan