Density‐dependent dispersal strategies in a cooperative breeder

Abstract

Dispersal is a key ecological process that influences the dynamics of spatially and socially structured populations and consists of three stages-emigration, transience, and settlement-and each stage is influenced by different social, individual, and environmental factors. Despite our appreciation of the complexity of the process, we lack a firm empirical understanding of the mechanisms underlying the different stages. Here, using data from 65 GPS-collared dispersing female coalitions of the cooperatively breeding meerkat (Suricata suricatta), we present a comprehensive analysis of the effects of population density, mate availability, dispersing coalition size, and individual factors on each of the three stages of dispersal in a wild population. We expected a positive effect of density on dispersal due to increased kin competition at high densities. We further anticipated positive effects of mate availability, coalition size, and body condition on dispersal success. We observed increasing daily emigration and settlement probabilities at high population densities. In addition, we found that emigration and settlement probabilities also increased at low densities and were lowest at medium densities. Daily emigration and settlement probabilities increased with increasing female coalition size and in the presence of unrelated males. Furthermore, the time individuals spent in the transient stage increased with population density, whereas coalition size and presence of unrelated males decreased dispersal distance. The observed nonlinear relationship between dispersal and population density is likely due to limited benefits of cooperation at low population densities and increased kin competition at high densities. Our study provides empirical validation for the theoretical predictions that population density is an important factor driving the evolution of delayed dispersal and philopatry in cooperative breeders.

Rank-Related Contrasts in Longevity Arise from Extra-Group Excursions Not Delayed Senescence in a Cooperative Mammal

“…At our study population in South Africa, we followed individuals from birth to death, observing behavior and group composition three times per week and collecting blood samples at regular intervals [13]. Our study area covers over 80 km 2 , and dispersal distances are short (mean: 2.2 km [14]), allowing us to detect dispersal with unusual resolution for a wild mammal.…”

“…While subordinates are more likely to disperse than dominants [13], this is unlikely to bias our estimates of longevity, for three reasons. First, dispersal distances are typically short (mean: 2.2 km, interquartile range: 1.08-2.66km [14]), facilitating detection of successful dispersal in our large study area (> 80km 2 ; [13]). Second, we closely monitor our study population for the establishment of new groups by dispersing subordinates.…”

African Wild Dog Dispersal and Implications for Management

“…Finally, dispersers continue in their fast and highly directional movements until they locate potential mates, in which case longer dispersal movements may be indicative of low occupancy rates, yielding fewer opportunities for the formation of new packs. Information on local population density and the distribution of resident individuals is important to fully understand dispersal processes and confirm or reject these hypotheses (Cozzi et al 2018, Maag et al 2018). Given the large spatial scale at which dispersal takes place, such information may only be collected through a well‐coordinated effort between national and international researcher institutions and government authorities (Kark et al 2015).…”

Perspectives from animal demography on incorporating evolutionary mechanism into plant population dynamics

“…Another key aspect of population dynamics that is often ignored in plant and animal IPMs alike is dispersal. Migration patterns have been shown to strongly affect phenotypic traits and vital rates and may play a key role in evolutionary dynamics (e.g., Maag et al , 2018). It is increasingly recognized that dispersal is not random but that certain genotypes or phenotypes are more likely to disperse than other (Edelaar & Bolnick, 2012; Ozgul et al , 2014; Deere et al ., 2017).…”