Patricia M. Harveson

Habitat use by ocelots in south Texas: implications for restoration

Abstract The ocelot (Leopardus pardalis) is an endangered cat native to south Texas. Urbanization and agricultural development have resulted in limited and fragmented habitat, making ocelot habitat restoration an important factor in the cats recovery. We evaluated the use of United States Department of Agriculture-Natural Resource Conservation Service (USDA-NRCS) soil surveys to identify potential restoration sites by examining ocelot habitat use in south Texas from 1982–1990. We analyzed an 8-year data set of ocelot radiotelemetry locations using Geographic Information Systems (GIS) and Baileys confidence intervals. Ocelots selected habitat with dense (>95%) canopy cover more than open (<75%) canopy cover. Ocelots also selected Camargo, Lardeo, Olmito, and Point Isabel soil series in greater proportion than available. The selected soils also represented 82% of the selected dense canopy cover areas. Our results suggest that USDA-NRCS soil survey maps can be used as a tool for identifying potential areas for ocelot habitat restoration.

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

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).

From the Field: Changes in ranges of Florida Key deer—does population density matter?

Abstract The relationship between population density and range size has long been debated. While many studies have documented varying responses in range size to changes in population densities, most have been the result of experimental manipulation. We examined the effects of long-term density changes in Florida Key deer (Odocoileus virginianus clavium) on range and core-area sizes. We radiocollared Key deer as part of 2 separate research projects conducted December 1968–June 1972, and January 1998–December 2001. We used a total of 96 (females, n=62; males, n=34) and 163 (females, n=88; males, n=75) radiocollared Key deer to calculate annual and seasonal ranges and core areas, respectively. Season and age were not important factors in describing ranges and core areas of Key deer, while sex and period (early vs. current study) were important. On average, male annual ranges (x̄=221 ha, current; x̄=388 ha, early) were greater than female annual ranges (x̄=42 ha, current; x̄=101 ha, early), which might explain higher male mortality due to roadkills. Early ranges and core areas were greater (≈2x) than current ranges and core areas. We suggest that increased deer densities may have resulted in a decrease in Key deer ranges. Other factors influencing changes in Key deer ranges included increased habitat quality and Key deer domestication over the last 30 years.

Toxic chemical wastes and the coincidence of carcinogenic mortality in Texas

Environmental‐justice proponents have argued that demographic factors unevenly affect the location of manufacturing and waste facilities and, thus, differences in exposure risks and outcomes. In this paper, statistical relationships among demographic factors, toxic chemical wastes released by Texas manufacturing facilities who participated in the Environmental Protection Agencys Toxics Release Inventory program in 1990, and carcinogenic causes of death were examined at the county level of analysis. Three types of carcinogenic death rates were regressed against the following county‐level variables: percent of the population under the age of 14, percent of the population 65 years of age and older, percent of population female in the childbearing ages of 15 to 44 years, percent Black population, percent Hispanic population, population density, percent of population employed in manufacturing industries, and per capita income. Results indicated that the elderly and young proportions of county population and t...

Assessing habitat relationships of mountain lions and their prey in the Davis Mountains, Texas

Abstract Availability and habitat use are central factors in the selection of prey by mountain lions (Puma concolor), and they are important for understanding predator–prey dynamics. We used an array of camera traps to evaluate the relative abundance and spatial distribution of mountain lions and their prey in the Davis Mountains of Texas. Resource selection was evaluated for four criteria: elevation, ecological system, fine-scale terrain ruggedness, and broad-scale terrain ruggedness. We used χ2 analysis to determine whether habitat was used in proportion to availability, and then we calculated a selection index with 95% confidence intervals using a Bonferroni adjustment. We found feral hog (Sus scrofa) to be the most abundant species, composing 23% of the total animals observed. Feral hog and gray fox (Urocyon cinereoargenteus) were the most widespread species, each observed at 33 of 38 camera locations. For each prey species evaluated, habitat use differed significantly from availability for at least one of the four resource criteria. Mountain lion use of resource criteria was not different from availability, except they avoided the second lowest class of broad-scale terrain ruggedness. With knowledge of mountain lion habitat use and the availability of prey, resource managers can better assess what effects mountain lion predation may have on a specific species, thereby allowing for better management of those species.

Characteristics of two mountain lion Puma concolor populations in Texas, USA

Influential factors associated with population dynamics of mountain lions Puma concolor include exploitation rates, prey availability, habitat structure and social structure. Throughout most of North America, mountain lion harvest is regulated by state or provincial quotas or is protected by federal laws. In Texas, however, they are not classified as a game or fur-bearing animal so their harvest is not regulated. To better understand the differences between population characteristics of mountain lions in west Texas (WTX) and south Texas (STX), we initiated two ecological studies. We captured, radio-marked and monitored mountain lions to ascertain survival, mortality factors, density, reproduction and population structure. We captured and monitored 19 and 21 mountain lions in the STX and WTX study sites, respectively. Average densities (No/100 km2) were different between our two study sites (STX = 0.269, WTX = 0.427) and were considerably lower than in previous studies. Mortality factors also differed between the two areas; in STX the causes were predominantly hunter harvest compared to trapping in WTX. Seasonal survival rates of mountain lions were lower during the general hunting season (STX = 0.783, WTX = 0.750) than during the non-hunting season (STX = 0.962, WTX = 0.931). Because population characteristics differed between the two genetically separated populations (Walker et al. 2000), resource managers should consider evaluating regional, rather than statewide management plans for mountain lions in Texas.

Comparison of Survival Estimates Using Age-Specific Mortality and Radiotelemetry Data for Florida Key Deer

Abstract Obtaining reliable survival estimates is important in the management of wildlife populations, particularly for the construction of computer simulation models. Many methods for estimating survival (e.g., radiotelemetry) are cost-prohibitive or time consuming. Life tables can provide survival estimates using data routinely collected by some management agencies. We calculated annual survival for Odocoileus virginianus clavium (Key deer) using age-specific mortality data. We compared our life-table estimates to those calculated from radiotelemetry data. Key deer survival estimates derived from life tables were similar to rates calculated from radiocollared deer. The only exception was for yearling/adult females on north Big Pine Key, where the life-table estimate was only slightly outside of the 95% confidence interval for the radiotelemetry estimate. Our results suggest that life tables based on age-specific mortality data can be a useful tool in estimating survival for Key deer. Comparing survival estimates from both methods allowed us to evaluate potential biases due to violation of assumptions associated with life-table calculations. While wildlife managers should be aware of the potential biases, age-specific mortality data may provide an adequate and cost-effective alternative for estimating survival.