Male–male and female–female dyads of two species of Phodopus, the Djungarian hamster, P. campbelli, and the Siberian hamster, P. sungorus, interacted daily for 10 min on each of 4 successive days. Animals were acclimatized to large habitats which contained small, defensible nest boxes. Real time behavioral records were kept of agonistic, social, and scent marking behaviors. The results indicated that there were major behavioral differences between P. campbelli and P. sungorus in their agonistic interactions with like-sexed conspecifics. Male P. campbelli were significantly more aggressive towards conspecific males than male P. sungorus, attacking (19.7 ± 2.2 vs. 9.6 ± 1.2) and biting (30.0 ± 4.6 vs. 12.7 ± 2.1) more often, and could inflict serious injury. Conversely, female P. campbelli were less aggressive than female P. sungorus towards like-sexed conspecifics, attacking (2.6 ± 0.7 vs. 7.5 ± 1.5) and biting (1.0 ± 0.4 vs. 2.4 ± 0.6) less frequently. The absolute levels of aggression were higher for males than for females although the magnitude of the difference was much less in P. sungorus than in P. campbelli. Dominant animals showed a tendency to spend most of the time available in the home area of the subordinate animal and to scent mark more frequently while there. The time distributions of dominant and subordinate animals within pairs (except for P. sungorus males) were significantly positively correlated. Dominant animals of both sexes scent marked with similar frequencies. When interpreted in light of the literature concerning the possible social structure of Djungarian hamster populations, this study suggests that the differences between the two species are sufficiently large that it is important to carefully distinguish between them in the published record.
Preimplantation Endocrinology in the Djungarian Hamster (Phodopus Campbelli) Progesterone, Estrogen, Corpora Lutea, and Embryonic Development1
