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Wildlife mortality from infrastructure collisions: statistical modeling of count data from carcass surveys
Author(s) -
Stevens Bryan S.,
Dennis Brian
Publication year - 2013
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/12-1052.1
Subject(s) - count data , wildlife , statistics , poisson distribution , data set , collision , poisson regression , magnitude (astronomy) , statistical model , point process , cox process , econometrics , geography , environmental science , ecology , mathematics , poisson process , computer science , biology , demography , population , physics , computer security , astronomy , sociology
Anthropogenic infrastructure is a mortality source for many vertebrate species. Mortality is often measured using periodic counts of carcasses or remains at infrastructure segments, and bias from carcass removal is estimated via field experiments with wildlife carcasses. We describe a model for combining removal experiment and carcass count data to estimate underlying process parameters using joint likelihood. In the model, the instantaneous number of carcasses present is a stochastic birth–death process with Poisson arrivals (carcass addition) and proportional deaths (removal of carcasses). The approach accommodates modeling heterogeneity in the addition and removal processes using generalized regression. Results of fitting the model to a Greater Sage‐Grouse ( Centrocercus urophasianus ) fence collision data set show that order of magnitude differences in expected carcass counts can be a function of spatial differences in removal and suggest caution for interpretation of many published studies. While the model assumption of negligible detection error may be tenable for some systems, the modeling framework provides a starting point for future state‐space versions incorporating detection error.