Survival, mortality, and life expectancy of Florida Key deer

Increases in motor vehicle traffic, habitat loss, and human-deer interactions due to urban development threaten the recovery and management of Florida Key deer (Odocoileus virginianus clavium). To evaluate these threats, we estimated current survival rates and compared them to historic estimates, evaluated the causes of mortality from 1966 to 2000, and determined life expectancy of deer from marked animals. We radiomarked Florida Key deer as part of 2 separate field studies (1968-1972, 1998-2000), in addition to collecting mortality data and survey estimates (1966-2000). We analyzed survival data from 314 (157 male, 157 female) radiomarked deer using a known-fate model framework in program MARK. We considered a suite of a priori models based on the biology and current knowledge of Florida Key deer, and ranked them using Akaike's Information Criterion (AIC(c)) model selection. Important factors explaining deer survival were sex and geographical location. Model-averaged annual male survival (0.412-0.842) was lower than female survival (0.695-0.888). Marked female deer (n = 35) lived an average of 6.5 years (maximum 19 years), while marked male deer (n = 43) lived an average of 2.9 years (maximum 12 years). Deer survival also increased as deer moved away from U.S. Highway I (US 1). Deer-motor vehicle collisions accounted for >50% of total deer mortality, half of which occurred on US 1. Annual deer mortality since 1972 has increased and is attributed to an increase in the deer population size (1972-2000, 240%). We recommend finding methods to reduce deer-motor vehicle collisions because of human safety concerns. As efforts to reduce deer-motor vehicle collisions continue, biologists need to address high deer densities in management of this locally abundant but endangered deer population.