Evidence of natal habitat preference induction within one habitat type

Abstract

Natal habitat preference induction (NHPI) is a mechanism for habitat selection by individuals during natal dispersal. NHPI occurs in wild animal populations, and evidence suggests it may be a common, although little studied, mechanism for post-dispersal habitat selection. Most tests of NHPI examine the influence of distinct, contrasting natal habitat types on post-dispersal habitat selection. We test the hypothesis that NHPI can occur within a single habitat type, an important consideration for habitat specialists. The Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is an endangered forest obligate restricted to a single mountain primarily within mixed-conifer forest. We test for NHPI by comparing intra-individual differences in natal and settlement habitat structure and composition to expected random pairwise differences. Dispersing juveniles appear to select settlement locations that are more similar to natal areas than expected in several forest structure and composition variables that include canopy cover and live basal area. Our results provide support for NHPI as a mechanism for post-dispersal habitat selection in habitat specialists that occupy a single vegetation community type.

Keywords: Arizona; habitat selection; habitat specialist; natal dispersal; natal habitat preference induction.

Figure 1.

Overview of Mt Graham red squirrel habitat above 2 348 m in elevation, burn severity and associated study areas in the Pinaleño Mountains, Arizona, USA. Natal and settlement sites obtained from radio-collared juveniles shown in grey and white circles, respectively, and straight-line dispersal vectors are indicated by black lines.

Figure 2.

Distribution of observed and expected intra-individual Euclidean distance scores between forest structure and composition at natal and settlement sites for juvenile Mt Graham red squirrels in the Pinaleño Mountains, Arizona, USA. Intra-individual Euclidean distance scores within 30 m ground-based plots, and within 30 and 100 m buffers summarized via lidar data are shown in relation to 10 000 iterations of randomized pairwise comparisons between natal and settlement sites for all animals (a), short-distance dispersers (b), and long-distance dispersers (c). Mean empirical intra-individual Euclidean distances between natal and settlement locations are indicated with a vertical line. (Online version in colour.)

Figure 3.

Relationship between intra-individual pairwise Euclidean distance scores between natal and settlement sites for juvenile Mt Graham red squirrels in the Pinaleño Mountains, Arizona, USA, and dispersal distance (m) for short-distance dispersers ≤150 m (a), long-distance dispersers moving > 150 m (b), and all animals (c). Lines represent linear models of the relationship between Euclidean distance scores and dispersal distance at three scales of forest structure and composition characterization: ground-based plot data (solid line), lidar data summarized within 30 m buffers (dotted line), and lidar data summarized within 100 m buffers (dashed line). (Online version in colour.)