Canine companions or competitors? A multi-proxy analysis of dog-human competition

Abstract

Globally, the place of dogs in the anthropogenic niche is varied, with dogs often tightly integrated into human communities, but sometimes pushed to the margins, and occasionally persisting as independent feral populations. Dog-human symbioses are correspondingly diverse, ranging from mutualistic to commensal to competitive. The Pacific Islands, and Polynesia in particular, offer a useful context in which to consider dog-human symbioses across varied socio-environmental settings. The translocation of domestic dogs across this oceanic region was underway more than two millennia ago, if not earlier, with dogs established on numerous Pacific Islands. However, occasionally dogs were subsequently extirpated, a situation often attributed to competition between dogs and their human managers. Here we focus on how the dog-human symbiosis shifted as colonists moved from the small, environmentally-circumscribed, islands of tropical central Polynesia, to the largest, most ecologically diverse landmasses in the region—the islands of Aotearoa New Zealand. We hypothesize that the mid-13th century settlement of Aotearoa New Zealand initially resulted in competitive release for Polynesian dogs (i.e., relaxation of competition with humans) but as large native prey were depleted, and human communities economically reorganised, dog-human competition arose anew. These two hypotheses are evaluated using: a) country-wide data on dog distributions and abundance over time; and b) a regionally focused analysis of dental markers relating to dog diet and health. Our results support the hypothesis of competitive release on entry to Aotearoa New Zealand; dogs were quickly distributed across the two main islands, onto many large offshore islands, and into varied ecological niches—where they were generally well represented and associated with human occupations. This situation appears to have been followed by interspecific competition midway through the Māori sequence (ca. AD 1450–1650), when both dog assemblages and dog abundances are poorly represented. From the mid-17th century, dog population rebound is suggested, possibly accompanied by new husbandry practices. These trends are not, however, well reflected in the regionally focused dental marker analysis, where good oral health and adequate nutrition are indicated. Published studies of dog coprolites and stable isotopes analyses help flesh out the dental analyses and point to avenues of future study. Our research gives new insights into variability in dog-human symbioses across the Pacific Islands and potentially elsewhere, with a particular focus on the conditions that give rise to competition and the value of multi-proxy analyses in unravelling these complex entanglements.