Key Deer Research Articles

Distribution and Abundance of Endangered Florida Key Deer on Outer Islands

ABSTRACT Status assessment of endangered Florida Key deer (Odocoileus virginianus clavium) is currently limited by a paucity of information regarding population estimates for outer islands, which collectively comprise approximately 70% of potential habitat within the Key deer range. Practical limitations and financial considerations render traditional survey techniques impractical for application on remote outer islands. Our objective was to evaluate the utility of infrared‐triggered cameras to estimate Key deer abundance on outer islands. We used digital infrared‐triggered cameras and mark‐resight methods to estimate Key deer abundance on 20 outer islands. Abundance estimates for primary subpopulations ranged from 15 to 16 for Howe Key, 5 to 10 for Knockemdown complex, and 13 to 17 for Little Pine Key. Other island complexes such as Ramrod Key, Water Key, and Annette complex maintain only small subpopulations (i.e., ≤5 individuals) and other previously inhabited island complexes (e.g., Johnson complex and Summerland Key) no longer maintain subpopulations. Key deer abundance was well below estimated carrying capacities on all outer islands, with larger natural populations occurring closest to Big Pine Key. Our results suggest that camera‐based surveys offer a practical method to monitor abundance and population trends of Key deer on outer islands. Our study is the first to estimate Key deer abundance in these areas using technically structured model‐based methods and provides managers with current and baseline information regarding Key deer subpopulations.

Effects of US 1 Project on Florida Key Deer Mortality

ABSTRACT Approximately 26% of annual mortality for the endangered Florida Key deer (Odocoileus virginianus clavium) occurs as deer‐vehicle collisions (DVCs) on the 5.6‐km section of United States Highway 1 (US 1) on Big Pine Key (BPK), but extensive urban development adjacent to sections of US 1 complicates efforts to reduce DVCs. Our objective was to evaluate the effectiveness of the US 1 Project (continuous 2.6‐km system of 2.4‐m fencing, 2 underpasses, and 4 experimental deer guards constructed on US 1 on BPK) in reducing DVCs along US 1. Deer used the underpasses all 3 postproject years (2003–2005); however, we observed higher underpass use in 2004 and 2005 compared to 2003. Exclusion fencing reduced deer intrusions onto the fenced section of US 1 during the 3‐year period (2003, n = 7 deer; 2004, n = 4; 2005, n = 12). With a reduction of deer intrusions onto this section of US 1, DVCs decreased in the fenced area by 73–100%; however, US 1 DVCs within the unfenced sections of US 1 also increased (40%) as expected. In controlling for effects of increasing deer density and traffic volume, study results suggest that highway improvements have decreased the net risk of DVCs along US 1, which indicates that use of deer fencing, deer guards, and underpasses is applicable in other urban communities experiencing unacceptable levels of DVCs.

Updated Distribution of the Lower Keys Marsh Rabbit

The Lower Keys marsh rabbit (LKMR; Sylvilagus palustris hefneri) is endemic to the Lower Keys of Florida and exists as a metapopulation in patches of salt-marsh–buttonwood transition zone, freshwater wetlands, and coastal beach berm vegetation (Forys and Humphrey 1996). Local LKMR populations interact through dispersing individuals, and patches undergo periodic local extinctions and recolonization (Forys and Humphrey 1999a). Much of the LKMR’s habitat has been lost or fragmented by human development over the past several decades, prompting the United States Fish and Wildlife Service (USFWS) to list the subspecies as endangered in 1990 (USFWS 1990). Knowledge of the distribution of occupied and potential LKMR habitat patches is critical to the design of recovery strategies for the subspecies. Historically, LKMRs occupied most, if not all, larger islands from Big Pine Key to Boca Chica Key, and may have occurred on Key West as well (DePourtales 1877, Layne 1974, Howe 1988, Lazell 1989; D. Stevenson, Felix Environmental Services, personal communication; Fig. 1). Although rapid habitat loss occurred in the 1970s and 1980s (USFWS 1997), little information is available on the LKMR’s distribution prior to 1988. The oldest known written records are anonymous notes dated 1968–1987 written on blue line photographs discovered at the National Key Deer Refuge in 2003. These records documented presence of LKMRs at 20 sites on Big Pine Key. Howe (1988) conducted the first published survey of the LKMR metapopulation by surveying 13 patches noted by J. Lazell (The Conservation Agency, unpublished data) and 3 additional patches. He reported that rabbits were absent from 4 of these patches, no longer occurred on Cudjoe Key, and were threatened by human activities in remaining patches. Forys (1995) completed a more comprehensive survey from 1991 through 1993. She identified 59 patches of occupied and potential (i.e., unoccupied, but apparently suitable) LKMR habitat. This survey included all but 2 of the patches noted by Howe (1988). LKMRs consistently occupied 19 of these patches over the course of her study, occupied 23 other patches in 1 survey, and did not occupy 17 patches. In 1995, Forys et al. (1996) discovered an additional 19 and 47 occupied and potential patches, respectively. Forys (1995) and Forys et al. (1996) found no extant populations between Big Pine and Sugarloaf keys. Based on these surveys and demographic data collected by Forys (1995), a population viability analysis (PVA) model suggested the metapopulation had a 100% probability of extinction in the next 50 years (Forys and Humphrey 1999b). Researchers have not formally surveyed the range-wide status and distribution of the LKMR since the mid-1990s. Managers charged with the recovery of this species need current data. Therefore, we surveyed potential LKMR habitat throughout the Lower Keys from 2001 through 2005. Specifically, our objectives were 1) to update the distribution and occupancy status of LKMR habitat patches, 2) to document patterns in patch occupancy from 2001 through 2005, and 3) to draw comparisons to previous formal and informal surveys.

Impacts of endangered Key deer hervivory on imperiled pine rocklands: a conservation dilemma?

In the lower Florida Keys, endangered Key deer (Odocoileus virginianus clavium) herbivory, along with fire, can affect pine rocklands, an endangered plant community. We compared pineland vegetation from three studies over approximately 50 years on four islands with either high or low deer density (historical analysis). We also compared extant vegetation samples between two islands with high or low deer density, which contained pinelands burned 10 years and 14 years prior to sampling and control areas (unburned for > 50yr). In addition, experimental deer exclosures and control plots established in pineland were prescribe burned and analyzed for deer effects on an island with high density of Key deer. The historical analysis suggests that, over time, deer-preferred plant species declined while less-preferred species increased, regardless of fire history on islands. The extant vegetation analysis suggests that fire and Key deer herbivory both reduce hardwood plant density and growth. Densities of deer-preferred woody species were higher on an island with low deer density than on an island with high deer density in burn treatments, but relatively similar in control areas. On the high deer density island, a fire effect was evident in that the control area had higher densities of woody species than burned areas, and herbaceous species richness was higher in the control area, indicating a possible refuge from deer herbivory. In deer exclosures, preferred woody species and herbaceous species tended to increase after fire, but decrease in adjacent open plots. Results suggest that Key deer herbivory, along with fire, shapes pine rockland plant communities, and that overbrowsing might have substantial impacts on preferred herbaceous and woody species in pinelands. Therefore, efforts could be confounded in managing both the endangered Key deer and the endangered pine rocklands that they affect.

Key Deer Impacts on Hardwood Hammocks Near Urban Areas

Abstract On islands in the lower Florida Keys, endangered Key deer (Odocoileus virginianus clavium) aggregate in urban areas where deer densities are high, potentially increasing browsing impacts in these areas. To quantify impacts, we compared plant densities and diversity in hardwood hammocks located adjacent to (urban) and distant from (exurban) developed areas on islands with high (>17 deer/km2) and low (<1 deer/km2) Key deer densities. Although we detected no differences in total plant densities or diversity on islands with high densities of deer, we observed lower mean (±SE) densities of deer-preferred plant species within reach of deer in hammock stands in urban areas (84.9 ± 35.9/ha) than exurban areas (694.5 ± 428.4/ha). No such patterns were evident on islands with low deer densities. We also experimentally tested deer browsing intensity on islands of high deer density using potted plants. We found that mean (±SE) browsing pressures (measured as proportion of leaves remaining on potted plants) w...

INTERISLAND DISPERSAL OF THE BLACK SALT MARSH MOSQUITO, OCHLEROTATUS TAENIORHYNCHUS (DIPTERA: CULICIDAE) IN THE FLORIDA KEYS

Mark-release-recapture experiments were conducted in 2001 and 2002 to determine whether Ochlerotatus taeniorhynchus, black salt marsh mosquitoes, were dispersing from uninhabited islands in the Key Deer National Wildlife Refuge to inhabited islands within Monroe County, Florida. An estimated 1,658,000 mosquitoes were marked during 2001, and an estimated 300,000 mosquitoes were marked during 2002. Recapture rates were 0.0061% and 0.0117%, respectively. Oc. taeniorhynchus disperse from uninhabited islands to other uninhabited islands and also to inhabited islands, namely, Big Pine Key and No Name Key.

Impacts of urbanization on Florida Key deer behavior and population dynamics

Rapid human population growth and urbanization have had a negative impact on species biodiversity. As competition for resources between man and wildlife continues, it is important to understand the effects of urbanization on species. Endangered Key deer ( Odocoileus virginianus clavium) are endemic to the Florida Keys which have undergone rapid human population growth and development over the past 30 years. Our study objectives were to evaluate the impacts of urban development on Key deer habitat use, population dynamics, behavior, and body mass. We used data from two comprehensive studies on Key deer spanning 30 years to evaluate these changes. Our results suggest that Key deer have become more urbanized, using urban areas more today than they did 30 years ago. Contrary to our predictions, survival was higher for more urban deer than for less urban deer. Problems still exist with mortality factors heavily impacting some portions of the deer population including lower survival associated with less urban male deer. Analysis of Key deer body mass also was converse to our predictions as deer weights appear to have increased over time. Collectively, our results suggest that over the past 30 years Key deer have become more urbanized and that deer plasticity has allowed them to adapt and persist in an urbanizing environment. However, the future ability of Key deer to persist in an environment with continued urban development is unknown. At some threshold, urban development would become unsustainable and unlike other forms of habitat change or environmental disturbances, urban development is in most cases irreversible requiring careful planning in habitat conservation strategies.

Urban wildlife management

Urban wildlife management

Relationships among Key deer, insect herbivores, and plant quality

AbstractDeer can have severe effects on plant communities, which in turn can affect insect communities. We studied the effects of Key deer herbivory on the incidence of insect herbivores that occur within deer habitats in the lower Florida Keys, within the National Key Deer Refuge (NKDR). We analyzed plant chemistry (tannins, nitrogen) and surveyed for the occurrence of insects (above the browse tier) among plant species that were either deer‐preferred or less‐preferred. Results indicated higher levels of foliar tannins on islands with fewer Key deer and larger amounts of foliar nitrogen on islands with a high density of Key deer. Consequently, leaf miners were significantly more abundant on islands with high deer density, irrespective of deer‐preference of plant species. On islands with a high deer density, incidence of leaves damaged by chewing insects was lower on preferred plant species but greater on less‐preferred species than on islands with fewer deer. No apparent patterns were evident in the distribution of leaf gallers among plant species or islands with different deer density. Our results imply that plant nutrition levels—either preexisting or indirectly affected by deer deposition—are more important than plant defenses in determining the distribution of insect herbivores in the NKDR. Although high densities of the endangered Key deer have negative effects on some plant species in the NKDR, it seems Key deer might have an indirect positive influence on insect incidence primarily above the browse tier. Further research is warranted to enable fuller understanding of the interactions between Key deer and the insect community.

Long-term Changes in Plant Communities Influenced by Key Deer Herbivory

The aim of the present study was to estimate changes in plant species composition in several forest communities caused by changes in endangered Key deer (Odocoileus virginianus clavium) densities in the National Key Deer Refuge in the lower Florida Keys. Baseline vegetation quadrats from a 1990 study were resampled in 2002 (the present study) in buttonwood transition, hardwood hammock, and mangrove wetland communities (all deer habitat) on 12 islands with low, medium, and high Key deer densities. On islands with high Key deer densities (>17 deer km−2), the relative densities of preferred plant species <1.2 m tall significantly decreased over time in each deer habitat, and nonpreferred species <1.2 m tall significantly increased in hammock and mangrove habitats. No significant changes were observed in densities of plant species <1.2 m tall on islands with low and medium Key deer densities (<8 deer km−2). Relative densities of preferred plant species >1.2 m tall (midstory/canopy) also significantly decreased in hammock on islands with high deer density, suggesting that heavy browsing is deterring plant growth/recruitment, thus already affecting regeneration of certain plant species into the midstory/canopy tiers. Plant species richness did not vary significantly between 1990 and 2002 for islands with high deer densities, but tended to increase slightly on islands with low deer density in buttonwood and hammock communities. Evidence from this study suggests that high densities of Key deer influence plant species composition on certain islands. We suggest that management plans for Key deer should incorporate both species protection components and population control techniques dependent on deer density-island associations.

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

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.

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

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 ni...

Fuel loads, fire regimes, and post-fire fuel dynamics in Florida Keys pine forests

In forests, the effects of different life forms on fire behavior may vary depending on their contributions to total fuel loads. We examined the distribution of fuel components before fire, their effects on fire behavior, and the effects of fire on subsequent fuel recovery in pine forests within the National Key Deer Refuge in the Florida Keys. We conducted a burning experiment in six blocks, within each of which we assigned 1-ha plots to three treatments: control, summer, and winter burn. Owing to logistical constraints, we burned only 11 plots, three in winter and eight in summer, over a 4-year period from 1998 to 2001. We used path analysis to model the effects of fuel type and char height, an indicator of fire intensity, on fuel consumption. Fire intensity increased with surface fuel loads, but was negatively related to the quantity of hardwood shrub fuels, probably because these fuels are associated with a moist microenvironment within hardwood patches, and therefore tend to resist fire. Winter fires were milder than summer fires, and were less effective at inhibiting shrub encroachment. A mixed seasonal approach is suggested for fire management, with burns applied opportunistically under a range of winter and summer conditions, but more frequently than that prevalent in the recent past.

The role of dispersal in Florida Key deer metapopulation dynamics

Metapopulation dynamics of species that occur in patchy or island subpopulations are an important consideration in the conservation of endangered species. Key deer ( Odocoileus virginianus clavium) are endemic to the Florida Keys and occur on 11 island-complexes in the Lower Keys from Big Pine Key to Sugarloaf Key. While deer numbers have increased notably, the majority of the population occurs on two of the islands, Big Pine and No Name Keys. Deer dispersal between islands is possible due to short distances between islands and shallow water. Key deer have been documented to actively disperse between islands but at very low rates (11% males, 3% females). However, increased population densities could possibly increase dispersal rates as island populations on Big Pine and No Name Keys approach carrying capacity. We examined the probability of deer colonization of peripheral islands using a sex- and stage-structured metapopulation model. Our objectives were to (1) evaluate the effects of distance and dispersal rate on Key deer island subpopulations and (2) estimate the probability of Key deer colonizing surrounding islands with viable populations. Results suggest that over the next 20 years, the Key deer population could colonize 6 of the 11 island-complexes with viable populations. However, of the remaining five islands, three lack the resources to support a minimum viable population, and while Cudjoe and Sugarloaf Keys have the potential to support >200 deer each, they are not projected to increase to above 50 deer by 2021 regardless of dispersal rate due to distance from source population.

Effects of Key deer herbivory on forest communities in the lower Florida Keys

Ungulate herbivory can have strong impacts on plant communities, but these impacts are rarely considered in recovery plans of endangered species. This study examined the effects of the endangered Key deer ( Odocoileus virginianus clavium) on its environment in the lower Florida Keys. The Key deer population has increased to over 700 deer from approximately 50 deer in the 1950s; however, approximately 75% of the population resides on only a few islands (Big Pine, No Name, Big Munson) where Key deer herbivory on forest communities may be substantial. Effects of deer herbivory on plant densities were estimated on these islands using vegetation quadrats in hardwood hammock, buttonwood transition, and mangrove wetlands and compared to nine other islands with intermediate or low deer densities. On islands with high deer density, densities of preferred woody plant species <1.2 m tall (within Key deer reach) were significantly lower than islands with lower deer densities, while densities of some nonpreferred species were significantly higher. Deer exclosures established in hardwood hammock on a high-density deer island revealed a mean increase in abundance/height of preferred woody species inside exclosures, while nonpreferred species significantly increased in open plots. We conclude that on high deer density islands, highly preferred plant species might eventually fail to regenerate and unpalatable plant species may become dominant. Careful criteria need to be developed to maintain Key deer numbers above an endangered species status yet below levels that are destructive to local forest species.

Domestication Threatens Key Deer

Conservation in PracticeVolume 6, Issue 4 p. 11a-11a Domestication Threatens Key Deer First published: 08 March 2006 https://doi.org/10.1111/j.1526-4629.2005.tb00129.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue4October 2005Pages 11a-11a RelatedInformation

Wildlife Loss through Domestication: the Case of Endangered Key Deer

Abstract: Wildlife extinction represents the ultimate failure of wildlife conservation. It has many causes, some of them natural, but is increasingly tied to anthropogenic factors. Wildlife loss via domestication, however, is rarely considered. We evaluated the potential for inadvertent domestication of wildlife by determining the effect of feeding and watering on Key deer (Odocoileus virginianus clavium) density, group size, and distribution. Key deer sightings were significantly higher in areas (42 ha) surrounding the households that provided food and water (0.18 deer/m;n =8) than in randomly selected areas (0.03 deer/m;t =3.82, 14 df, p =0.002). Average distance to a household providing food and water decreased logistically as group size increased, and large groups (&gt;2 individuals each) were observed more frequently in areas where food and water were provided (27.5%) than in the randomly selected areas (7.5%). The incidence of large groups outside feeding areas (7.5%), however, was similar to the incidence of large groups during early urbanization (5.1%; 1968–1973). Our results suggest illegal feeding caused changes in density, group size, and distribution indicative of domestication. Because fresh water and food were primary selective pressures for Key deer before illegal feeding and watering, genetic changes may occur in the future. For those who value “wildness” in wildlife, domestication of wildlife species is a serious problem that must be addressed.

Changes in ranges of Florida Key deer—does population density matter?

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 (=221 ha, current; =388 ha, early) were greater than female annual ranges (=42 ha, current; =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.

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

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).

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

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.