Philip A. Frank

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 Akaikes Information Criterion (

HABITAT‐USE PATTERNS OF FLORIDA KEY DEER: IMPLICATIONS OF URBAN DEVELOPMENT

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Comparison of Camera and Road Survey Estimates for White-Tailed Deer

) 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 1 (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.

POPULATION DENSITY OF THE ENDANGERED FLORIDA KEY DEER

Abstract Urban development in the Florida Keys, USA, mandates an understanding of how habitat requirements for Florida Key deer (Odocoileus virginianus clavium) interact with vegetation changes caused by development. Our study objectives were to (1) determine Key deer habitat use at different spatial scales, (2) evaluate vegetation changes and identify vegetation types most threatened by development, and (3) provide guidelines to direct land acquisition programs in the future. We identified 6 vegetation types: pineland, hammock, developed, freshwater marsh, buttonwood, and mangrove. Key deer (n = 180; 84 F, 96 M) preferred upland vegetation types (>1 m above mean sea level; pineland, hammock, developed) and avoided tidal or lower-elevation areas (<1 m above mean sea level; freshwater marsh, buttonwood, mangrove). Analyses of Geographic Information System (GIS) coverages suggested that historical development impacted near-shore habitats while recent trends pose a greater risk to upland areas (pineland, hammock). Because uplands are preferred by Key deer, conservation measures that include land acquisition and habitat protection of these areas may be needed.

SOURCE–SINK DYNAMICS OF FLORIDA KEY DEER ON BIG PINE KEY, FLORIDA

Abstract Wildlife managers require reliable, cost-effective, and accurate methods for conducting population surveys in making wildlife management decisions. Traditional methods such as spotlight counts, drive counts, strip counts (aerial, thermal, infrared) and mark–recapture techniques can be expensive, labor-intensive, or limited to habitats with high visibility. Convenience sampling designs are often used to circumvent these problems, creating the potential for unknown bias in survey results. Infrared-triggered cameras (ITCs) are a rapidly developing technology that may provide a viable alternative to wildlife managers because they can be economically used with alternative sampling designs. We evaluated population-density estimates from unbaited ITCs and road surveys for the endangered Florida Key deer (Odocoileus virginianus clavium) on No Name Key, Florida, USA (461-ha island). Road surveys (n = 253) were conducted along a standardized 4-km route each week at sunrise (n = 90), sunset (n = 93), and nighttime (n = 70) between January 1998 and December 2000 (total deer observed = 4,078). During this same period, 11 ITC stations (1 camera/42 ha) collected 8,625 exposures, of which 5,511 registered deer (64% of photographs). Study results found a difference ( P < 0.001) between methods with road-survey population estimates lower (76 deer) than ITC estimates (166 deer). In comparing the proportion of marked deer between the 2 methods, we observed a higher ( P < 0.001) proportion from road surveys (0.266) than from ITC estimates (0.146). Spatial analysis of deer observations also revealed the sample area coverage to be incongruent between the 2 methods; approximately 79% of all deer observations were on urban roads comprising 63% of the survey route. Lower road-survey estimates are attributed to 1) urban deer behavior resulting in a high proportion of marked deer observations, and 2) inadequate sample area coverage. We suggest that ITC estimates may provide an alternative to road surveys for estimating white-tailed deer densities, and may alleviate sample bias generated by convenience sampling, particularly on small, outer islands where habitat and/or lack of infrastructure (i.e., roads) precludes the use of other methods.

Hurricane impacts on key deer in the Florida Keys

Abstract With decreased illegal hunting and better habitat conservation, the Florida Key deer (Odocoileus virginianus clavium) population grew from an estimated 25–50 animals in the late 1940s to approximately 200 animals on Big Pine and No Name keys, Florida, USA, by 1971, the last official survey. U.S. Fish and Wildlife Service (USFWS) trend data indicate that the deer population continued to increase after 1971; however, current deer density estimates are necessary for the proposed reclassification of the Key deer from endangered to threatened. Our study objectives were to (1) obtain current population estimates of Florida Key deer and compare these to historical estimates, (2) evaluate survey methods (USFWS mortality and deer counts) in detecting changes in population trends, and (3) outline a protocol for future monitoring. Road counts (n = 889) were conducted from January 1971 to December 1971 and January 1976 to December 2001 on Big Pine and No Name keys. From mark–recapture data, we estimated that the Key deer population on these 2 islands increased by 240% between 1971 and 2001 (2001 estimate: 453–517 deer). Trend data indicated that annual deer mortality was a function of deer density or population size (rs = 0.743). We compared the annual finite rate of increase (R) from USFWS annual deer counts and mortality data (R = 1.053–1.065) to mark–recapture studies (R = 1.038) and found them to be similar (P = 0.66–0.67). This similarity suggests that all 3 methods (USFWS deer counts and mortality data, and mark–recapture data) can be used to monitor changes in Key deer density.

Tick Paralysis of a Snake Caused by Amblyomma rotundatum (Acari: Ixodidae)

Abstract The endangered Florida Key deer (Odocoileus virginianus clavium) is endemic to the Florida Keys, Florida, USA, with Big Pine Key (BPK) supporting most (approx 60%) of the population. Habitat loss and fragmentation have altered the amount of available habitat, creating areas of varying suitability; north BPK (NBPK) is believed to contain more optimal habitat than south BPK (SBPK), which is more developed and fragmented. We evaluated the source–sink dynamics of Key deer using a sex- and stage-structured, stochastic matrix model. Model results indicated that the NBPK population of Key deer was increasing (λ = 1.02), whereas the SBPK population was decreasing (λ = 0.87). Without dispersal from the north, the SBPK population has a 97% probability of falling below 25 individuals (quasi-extinction threshold) in the next 20 years. The higher risk to Key deer in SBPK can be explained by relative habitat-quality differences between the 2 areas. House density, amount of roads, number of fences, and amount of development were all greater in SBPK. Collectively, study results indicate that SBPK can be described as an ecological sink with a nonviable population supplemented by deer dispersal from NBPK (source). Care should be taken to preserve the source population and its habitat. Thus, we propose limiting future development in NBPK (high-quality source habitat). The US 1 highway corridor project has the potential to decrease Key deer mortality due to vehicle collisions, and we recommend that future management goals continue to address mortality factors on SBPK (low-quality sink habitat).

Population Status and Habitat Selection of the Endangered Key Largo Woodrat

The landing in the Florida Keys of Hurricanes Georges (Category 2) in 1998 and Irene (Category 1) in 1999, in combination with an ongoing radiotelemetry study of Florida Key deer (Odocoileus virginanus clavium), offered a unique opportunity to evaluate the impacts of natural disturbances on Key deer. We relocated 53 deer (female, n = 29; male, n = 24) during Hurricane Georges and 45 deer (female, n = 27; male, n = 18) during Hurricane Irene. One adult male drowned due to Hurricane Georges ( 15 ppt). In some cases, water-hole suitability did not improve until several weeks or months later. Our study suggests that mild to moderate hurricanes (Category 1-2) have little direct impact on the survival of Key deer; however, stronger storms (>Category 3) might have a greater impact due to stronger winds and greater storm surges (>3.5 m).

Updated Distribution of the Lower Keys Marsh Rabbit

Abstract A lethargic southern black racer, Coluber constrictor priapus Dunn and Wood, wild-caught in the Florida Keys, Monroe County, FL, was found to be paralyzed by the bite of a female ixodid tick, Amblyomma rotundatum Koch (Acari: Ixodidae). Removal of the tick restored the snake to normalcy within 18 h. Other, earlier reported cases of tick toxicosis in reptiles are reviewed and clarified. Evidently, the present incident is the only reported case of tick paralysis in a poikilotherm found in a natural setting.

Reintroduction of Lower Keys Marsh Rabbits

Abstract Over the last two decades, declines in trap success, stick-nest density and population density estimates have fueled concerns that the federally endangered Key Largo woodrat (KLWR, Neotoma floridana smalli) population is declining. Information on the current population status and habitat selection of KLWR is needed in the recovery of this population. We trapped on 60 (1-ha) randomly-placed grids (20 grids in each of three hardwood hammock age-classes). Grids were trapped from March–September 2002 and April–August 2004. Population estimates for the two trapping periods were 106 (95% ci 30–182) and 40 (95% ci 5–104) individuals, respectively. Greater than 80% of all KLWRs captures occurred in the young hammock age-classes (disturbed after 1971). Young hammocks were characterized by a more open canopy, smaller overstory trees, fewer logs, greater dispersion of overstory trees and a different species composition than old and medium age hammocks (P < 0.024). Contrary to previous research, KLWRs were found to nest in rock piles and garbage piles more than other materials. Results from this study suggest the KLWR population is critically low and management efforts should focus on the creation and restoration of young hammock habitats.