Recolonization of River Otters in the Grand
Canyon: An Individual-based Model

Description: 
River otter Lontra canadensis ranges in North America were reduced significantly because of pollution, urbanization, and over harvest. Numerous reintroduction programs have been initiated, often with limited success. Recently, groups have proposed to reintroduce river otters to the Grand Canyon. This program would be costly and logistically complicated. Therefore, the feasibility of natural recolonization should be assessed. We developed a spatially explicit, individual-based model to evaluate potential river otter dispersal from known populations. The model uses a population matrix consisting of individual otters at observed densities, male-female ratios, and age structures. We modeled variations in survival, reproduction, and dispersal probability and distance. Each year otter dispersal and reproduction results in colonization of new areas. Our model indicated that natural recolonization is possible from a demographic and biological perspective, however, increasing work to estimate otter movements across landscape types and areas impacted by human alteration is critical to producing robust probabilities of river otter dispersal, and targeting restoration efforts to the most critical threat(s) to river otter colonization.

Dates:
July 2001 through August 2001

Funding Sponsor:
River Otter Alliance/Ocean Journey Aquarium

Principal Investigator:
Nathan Nibbelink

Co-Principal Investigator:
M. BenDavid

Other personnel:
None