Social monogamy in the noki or dassie-rat ( Petromus typicus) in Namibia

Abstract

The noki or dassie-rat ( Petromus typicus) is a little-studied diurnal hystricognath rodent endemic to rocky outcrops in south-western Africa. An intermittent study in Namibia of 11 radio-tagged individuals, with over 250 h of direct observation, was done between 2000 and 2004 to document their basic natural history, including their social organization. The study was terminated when noki numbers collapsed, probably due to predation by an expanding population of black mongooses ( Galerella nigrata) that was unintentionally provisioned with food at a nearby eco-tourist lodge. Male and female adults were distributed as monogamous pairs on home ranges that were similar in size and shape. The pair bond was strong, with many coordinated behaviours. Reproduction was seasonal with litters of single highly precocial young. Multiple generations remained on the parental home range without significant aggression. Most aggression was between adult males, while adult females showed tolerance towards each other and intruding adult males. Although noki social monogamy is probably the result of male mate guarding, considerable paternal care was observed, including allogrooming and vigilance against predators. Nokis have a relatively low metabolic rate and numerous thermoregulatory behaviours that suggest that nocturnal huddling by the male with his mate and young may be an important factor in the evolution of their social monogamy.