ORIGINAL PAPER Multiple socioecological factors influence timing of natal dispersal in kangaroo rats Andrew J. Edelman Received: 24 May 2013 /Revised: 20 March 2014 /Accepted: 21 March 2014 /Published online: 10 April 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Natal dispersal is an important event in the life history of many species. Timing of natal dispersal can influ- ence survivorship and subsequent reproductive success. A variety of individual proximal factors determine if and when offspring disperse from the natal territory by influencing the costs of dispersing and the benefits of delaying dispersal. I examined the influence of multiple factors on dispersal age in the banner-tailed kangaroo rat (Dipodomys spectabilis), a solitary species lacking extreme sex-biased dispersal. I used an information theoretic approach to compare Cox propor- tional hazards regression models of dispersal age for 121 offspring over a 3-year period consisting of low and high population densities. The top-ranked models indicated that dispersal age was influenced by a combination of socioecological factors related to resource competition, envi- ronmental conditions, kin competition, and a lesser extent sex. Circumstances that likely reduced the probability of success- ful dispersal such as intense resource competition at high population density and being born earlier in the breeding season when environmental conditions were poor lead to longer delays in natal dispersal. Offspring in larger litters also dispersed earlier possibly to avoid competition with kin. Sex was weakly supported in top models but may only influence dispersal age at high population densities. These results sug- gest that the proximal factors that trigger dispersal are influ- enced by a combination of multiple effects related to the costs of dispersing and the benefits of remaining at home, even in species that do not form long-term social groups or have extreme sex-biased dispersal. Keywords Delayed dispersal . Habitat saturation . Juvenile dispersal . Philopatry . Sibling competition Introduction The permanent movement of offspring away from the parents’ territory, frequently called natal dispersal, is a widely observed phenomenon in animals. Natal dispersal is an important mech- anism for movement of genes and individuals across the landscape and can have strong effects on population dynam- ics, spatial distributions, and genetic structure (Clobert et al. 2001). The evolutionary causes for natal dispersal have re- ceived much attention and include inbreeding avoidance, reduction in competition, and environmental stochasticity (Moore and Ali 1984; Waser 1985; Chepko-Sade and Halpin 1987; Lambin et al. 2001; Perrin and Goudet 2001). The proximal causes of natal dispersal are less well known but are important to understanding the variation in this behavior within and among species. In particular, most research have focused on the factors that determine whether offspring re- main philopatric or disperse (Solomon 2003; Ekman et al. 2004); however, fewer studies have explored what factors regulate the exact timing of natal dispersal (Nunes and Holekamp 1996; Edelman 2011b; Waser et al. 2013). Proximal factors that determine if and when offspring disperse are generally classified as socioecological or phys- iological. Socioecological factors that can trigger or delay natal dispersal include population density, habitat quality, climate, conspecific aggression, and competition, whereas physiological factors may be related to sex, condition, size, and hormone concentrations (Holekamp 1986; Nunes and Holekamp 1996; Nunes et al. 1997; Smale et al. 1997; Alonso et al. 1998; Belthoff and Dufty 1998; Lambin et al. 2001). While the role that individual factors play in influencing dispersal is often studied in isolation, a Communicated by P. B. Banks A. J. Edelman (*) Department of Biology, University of West Georgia, Carrollton, GA 30118, USA e-mail: aedelman@westga.edu Behav Ecol Sociobiol (2014) 68:1123–1131 DOI 10.1007/s00265-014-1723-x