Internal and external factors affect pair mate proximity in captive coyotes, Canis latrans

A pair bond is a long-term social relationship between two unrelated individuals of the opposite sex that persists outside of the breeding season. The strength of a pair bond is often linked to behavioural and physiological components, such as behavioural synchrony and hormonal status, and can be measured across timescales, contexts and species. Pair mates that spend more time in proximity and that engage in the same activities are often more strongly bonded than pair mates that behave independently. Thus, the objectives of this study were to determine whether the amount of time that canid pair mates spend in proximity provides an index for the strength of their pair bond and whether pair bonds are dynamic or static across time and other factors. Coyotes exhibit pair-bonding behaviour in the form of territorial defence and biparental care and therefore make an excellent model for our objectives. We fitted captive coyote pair mates with proximity-tracking collars and collected faecal samples to quantify synchronous behaviour and hormonal status. We measured pair mate proximity across reproductive seasons (breeding versus nonbreeding), pair bond tenures (newly paired, 1–2 years paired, 5+ years paired) and times of day (dawn, day, dusk, night). We found that dusk was an important temporal window for quantifying pair mate proximity because dusk was the time when pair mate proximity significantly differed according to reproductive season or pair bond tenure. We detected marginally higher faecal progesterone levels in female coyotes during the breeding season, relative to the nonbreeding season, but we did not find differences across other hormone metabolites assessed. Female faecal progesterone metabolite levels were the only hormone significantly correlated with proximity behaviour outcomes. These results suggest that the amount of time that coyote pair mates spend in proximity can provide an index for the strength of their pair bond and that these pair bonds are dynamic and can be influenced by internal and external factors.