Acoustic territorial signaling in a small, socially monogamous canid

A Review

When an animal actively defends all or parts of its home range against intruders, the animal is considered territorial. Since there is a cost to being territorial by expending time and energy warding off opponents, there is variation in the degree of territoriality within species and between sexes. Animals can defend territories using physical contact, or passively by using vocal signals to announce the borders of their territory. By studying signaling behavior, it allows researchers to examine the territoriality of a species. In this study, researchers examined the territorial nature of the swift fox, Vulpes velox.

In the study, researchers examined to what extent the monogamous foxes used long ranging barking sequences in defense of their home ranges. The study was specifically done during mating season because it was believed that at this time of year the foxes would benefit most from territoriality. The researchers hypothesized that home range cores will be exclusive to mated pairs. If the foxes were using barking signals for territorial defense, then it was predicted that these calling behaviors will be more concentrated in the core of the home range compared to edge areas that are likely to be shared with neighbors. Additionally, the researchers used recordings of fox barking sequences to simulate intrusions of the home range core. It was predicted that the foxes would respond to intrusions at the core, but not when recordings were played on the edges at territorial overlaps.

The results of the study provided evidence for territorial defense in the swift fox species. According to the results, male foxes were most likely to produce barking sequences when intruders were within the 50% core area contour of their home range. Additionally, the male foxes displayed the most intense barking sequences and responded more quickly when recorded barking was played within the 50% core area as opposed to outside of this area. The results suggest that the vocalizing fox is willing to defend the core of their home range and possibly risk physical contact if an intruder is within this certain area. According to the researchers, there was some evidence of direct mate guarding, but it was more likely that the males foxes were defending the area where their mating partner spent the most time (home range cores and dens), and thus indirectly defending their mates.

This study on territorial signaling in the swift fox extends what was discussed in class about territory signals. According to the lecture, a territory is defined as a fixed area from which intruders are excluded by an owner using advertisement, threat, and attack. In this particular fox species, the defended territory seemed to include areas within a 50% contour line around the core of a home range. Additionally, owners of a territory are likely to continue to defend it because of the possible fitness benefits to be gained and the high cost to losing the territory. With respect to the swift foxes, the study was conducted during mating season when males were expected to be most territorial. As a monogamous species, the male foxes presumably risked losing their only mate if they failed to defend the core of their home range.

DARDEN, S. K., DABELSTEEN, T. (2008) Acoustic territorial signaling in a small, socially monogamous canid. Animal Behavior, 75, 905-912.