Natal Dispersal by Pygmy Rabbits (Brachylagus idahoensis)

• Published in: Journal of mammalogy 2009-04, Vol.90 (2), p.363-372
• Main Authors: Estes-Zumpf, Wendy A., Rachlow, Janet L.
• Format: Article
• Language: English
• Subjects: Age; Animal behavior; Animal ethology; Average linear density; barriers; Biological and medical sciences; Birds; Body condition; Body size; Brachylagus idahoensis; Breeding seasons; Burrows; Conservation; Dispersal; Dispersal behavior; Feature s; Fundamental and applied biological sciences. Psychology; Gravel; Habitat; Habitat conservation; Habitats; lagomorphs; Land management; Mammalia; Mammalogy; Mammals; Mortality; Perennial streams; philopatry; Predation; Psychology. Psychoanalysis. Psychiatry; pygmy rabbit; Rabbits; radiotelemetry; Sex; sex-bias; Streams; Studies; survival; Vertebrata; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Wildlife habitats; Young animals
• ISSN: 0022-2372; 1545-1542
• DOI: 10.1644/08-MAMM-A-078.1

Multiple factors likely influence natal dispersal behavior of juvenile mammals, which is typically male-biased. Because of their small body size and specific habitat requirements, pygmy rabbits (Brachylagus idahoensis) are expected to exhibit limited dispersal. We predicted that dispersal would be male-biased, that juveniles born later in the year would disperse farther, and that juveniles would be more likely to disperse away from areas of higher habitat saturation. We used radiotelemetry to study dispersal of 61 juvenile pygmy rabbits (31 males and 30 females) from shortly after emergence from natal burrows (April–July) to the beginning of the next breeding season (mid-March) during 2004–2006. Juveniles dispersed before 12 weeks of age, and typically completed dispersal movements within 1 week. Both sexes exhibited a high rate of dispersal (males = 90%; females = 80%); however, juvenile females settled more than 3 times farther from their natal areas than males. Median natal dispersal distances for males and females were 1.0 km (range = 0.03–6.5 km) and 2.9 km (range = 0.02–11.9 km), respectively. Dispersing juveniles crossed gravel roads and perennial streams; however, rabbits tended to initiate dispersal movements away from nearby streams. Mortality rates for male and female juvenile rabbits were 69.2% and 88.5%, respectively, and were highest during the first 2 months after emergence from the natal burrow. We found no evidence that date of emergence, body condition, or habitat saturation influenced dispersal frequency or distance in juvenile pygmy rabbits. Results indicate that pygmy rabbits are capable of dispersing long distances and suggest that their conservation will require land management at broader spatial extents.