Conservation Research Laboratory: General Conservation Projects

Melissa Merrick

Proximate cues and ultimate consequences for natal dispersal and settlement in an altered forest landscape: influence of experience, behavior, and habitat
  • Time Period: May 2010 - July 2016

  • Location: The Pinaleño Mountains, AZ, U.S.A.

Major Questions: I am interested in factors influencing animal movements and habitat selection in the face of landscape alteration and fragmentation. Movement via natal dispersal is an important ecological mechanism contributing to gene flow, population structure and population dynamics, and guards populations against local extinction. Natal dispersal includesthree stages: emigration, transience and exploration, and immigration and settlement. Whether an individual disperses, if it disperses how far it travels, how many places it explores, and where it settles is highly variable and is conditioned upon many factors including individual condition, local population density, sex ratios, resource abundance, experience in the natal area,habitat fragmentation, and individual behavior differences. Previous studies have shown thatexperience in the natal area provides individuals with important habitat cues which aid in deciding upon where to settle and also leads to variation in settlement patterns. Individual behavior differences may play a role in dispersal distance and settlement decisions, including decision rules individuals employ when selecting a place to settle. Local density of conspecifics and associated sex ratios may influence male settlement decisions, whereas female settlement decisions may be more driven by available food resources. Increasingly, habitat fragmentation is alsobecoming an external factor influencing dispersal decisions and evidence suggests that small mammals dispersing through a fragmented habitat matrix tend to disperse further and explore less than individuals in contiguous habitat. I am testing several hypotheses related to natal habitat preference induction, behavioral phenotypes, decision rules, and habitat fragmentation and their influence on natal dispersal, especially transience and immigration.

Some of my main research questions include: Do natal habitat cues (e.g. habitat structure, associated microclimate, and food availability) influence where settlement occurs? Do individual behavior differences (behavioral phenotypes) influence exploratory movements, decision rules, dispersal distance, and survival? Does forest fragmentation influence decision rules, settlement choices, and survivorship?

Major Findings To Date: Compared to non-peripheral red squirrel populations, dispersal in MGRS is sex-biased and exploration movements and settlement distances are far greater. Individual behavior differences explain variation in dispersal distances - active, aggressive individuals tend to disperse longer distances compared to less active, docile individuals. Natal habitat structure may play a role in cueing dispersers in on locations in which to settle. Forest structure derived from remotely sensed LiDAR data (e.g. canopy cover, basal area of live trees) in an individual’s natal area is more similar to forest structure at an individual’s settlement location compared to random locations. Further analyses are underway.

Check out our recent findings on how dispersing juveniles respond to burn severity and fuels reduction treatments - our work funded by the Joint Fires Science Program - Graduate Research Innovation Award - here.
See below for dissertation publications-


Publications from dissertation research:
Merrick, M. J. and J. L. Koprowski 2017. Circuit theory to estimate natal dispersal routes and functional landscape connectivity for an endangered small mammal. Landscape Ecology DOI 10.1007/s10980-017-0521-z. PDF of Article
Merrick, M. J. and J. L. Koprowski 2017. Should we consider individual behavior differences in applied wildlife conservation studies? Biological Conservation 209: 34-44. PDF of Article
Merrick, M. J. and J. L. Koprowski 2016. Altered natal dispersal at the range periphery: the role of behavior, resources, and maternal condition. Ecology and Evolution 00:1-15. doi: 101002/ece3.2612. PDF of Article
Merrick M. J. and J. L. Koprowski 2016 Evidence of natal habitat preference induction within one habitat type. Proceedings of the Royal Society B 283: 20162106. PDF of Article