Circuit theory to estimate natal dispersal routes and functional landscape connectivity for an endangered small mammal

Abstract

Natal dispersal links population dynamics to landscape connectivity. Understanding how organisms perceive barriers to movement, or landscape resistance, during natal dispersal is important to conserve and manage populations threatened by fragmentation and habitat loss. We aimed to (1) model probability of landscape use by an endangered small mammal (Tamiasciurus hudsonicus grahamensis) in the Pinaleno Mountains, Arizona, USA as a function of forest structure at the population and intra-population level, (2) identify potential natal dispersal pathways between natal and settlement locations based on landscape resistance scenarios, and (3) assess which resistance surface best represented observed exploration, dispersal, and settlement. We modeled probability of habitat use via used and available animal locations. We developed three landscape resistance scenarios to represent individual differences in perceived resistance. We used circuit theory to identify potential long-distance dispersal pathways and to assess which resistance scenario best represented observed forest use and settlement. Top probability of forest use models included physical landscape features, forest structure, and burn severity. Composite connectivity models, created from multiple resistance scenarios, identified areas that may promote long distance dispersal movements. Connectivity models developed from only natal focal nodes allowed for assessment of resistance scenarios; a non-linear, negative-exponential relationship between probability of use and resistance best represented observed exploration and settlement. Circuit theory is a useful tool to identify potential small mammal movement pathways when high temporal resolution movement data are limited, and for assessing how well resistance scenarios represent observed settlement patterns.