The emergence of ungulate type mammals is thought to have occurred during the
mid-Tertiary period based upon the fossil record for the “Old World” tropics.
The deer present in this environment played a modest ecological role at best.
(Geist, V.) Consistent with the tropics were areas of nutrient lacking or
leached soils. Due to the climate and weather patterns associated with the lower latitudes, some species of deer adapted to a fertile land surfaces that have been inundated with nutrient rich silt and loess from glacial actions, floods, wild fires, and avalanches. Constructive and destructive happenings have been the driving forces behind the evolution of the deer. Fossil evidence also suggests that deer overall did not flourish in a mature, species rich environment, but rather in a younger type of new growth area. Therefore, Artiodactyla of North America evolved as an opportunistic species taking advantage of high nutrient food surpluses that existed. The deer’s big appetite for highly digestible nutrient rich forage apparently drove its evolution. (Geist, V.)
Even toed vs. odd toes ungulates
The even toed ungulate (Artiodactyla) is named for having two or four digits. The Key deer may be referred to as having a cloven hoof (ungulate) with two toes. Observed on the “New World” deer the third and fourth digits are well developed but the second and fifth are present only as distal ends. The first digit is entirely absent. V. Geist presents the evolution of the two subfamilies. Old World Cervidae vs. New World. Perissodactyla, the odd toed ungulates, consist of a small order of herbivores that are distinguished from Artiodactlya by the presence of a prominent third digit. The horse family (Equida) has only one functional toe whereas the rhinoceros bears the majority of body mass on three digits. The lighter faster mammals run on only one (horse) or two (deer) toes. Of the two orders, Artiodactyla is the most successful based upon the diversity of species. Through time the diversity of Perissodactyla has diminished.
Taxonomy of Key Deer
Kingdom- Aniamalia
Phylum- Chordata
Class- Mammalia
Order- Artiodactyla
Family- Cervidae
Genus- Ordocoileus
Species- Virginianus
Subspecies- Clavium
Description of Key Deer
The Florida Key deer is the smallest species of Virginia White-Tailed deer in the United States. Mature male Key deer range in weight from 55 lbs. to 75 lbs. (24.9 kg- 34 kg) and measure 25 in. to 30 in. (63.5 cm-76.2 cm) at the shoulder. Female weight ranges from 45 lbs. to 65 lbs (20 kg – 29.5 kg). As compared to the white-tailed deer (Ordocoileus Virginianus) Key deer have characteristics of a stockier body, shorter legs, and a wider skull. The coat varies from a deep reddish brown to a gray color. The fact that Key deer are proportionally smaller than the neighboring white-tail relative found at greater latitudes clearly resembles Bergmann’s Rule. (Northern White-tails typically stand 40 in. (101.6 cm) at the shoulder and weigh less than 160 lbs. (72.6 kg)). Bergmann’s Rule states that body mass of a geographic race is in direct relation to the North/South distance form the equator. (Rue, L.) The rule does vary according to the opportunistic feeding behavior of deer. A preferred, abundant food source must be present to meet the nutritional needs. If not, body mass and volume decrease. To ensure that the forage is properly digested Key deer are equipped with specific teeth to increase mechanical digestion. Premolars and molars are permanently fixed to the mandible and maxilla. Canines are absent and incisors are located on the anterior end of the mandible only.
Digestive System/Diet
The digestive system is adapted for the fibrous diet of plant material. The ruminant four-chambered stomach must meet the energy requirements of a grazing ungulate by absorbing the maximum of nutrients while leaving little to waste. Mechanical digestion in the mouth is vital to the diet of all deer. Key deer along with other Order of Artiodactyla are known for their cud chewing. A symbiotic relationship exists with deer and the bacteria and protozoa found in the first chamber (rumen). The bacteria aid in the formation of a cud that can be regurgitated at a later time for post-mastication. This adaptation also aids as a survival strategy by allowing deer to be more receptive to predation during grazing. The re-chewed cud (now referred to as pulp) enters the reticulum, omasum, and finally the abomasum (true stomach for chemical digestion). The Florida Key deer’s primary food source is the red mangrove, black mangrove, Indian Mulberry, Silver and Brittle Thatch Palm fruits, Blackbead, grasses, Pencil Flower, Acacia, and Wild Dilly fruits. Precipitation influences what plants are grazed upon. During a drought plants typically left alone become a staple food source.
Habitat/Range
Key deer are restricted to Monroe County, Florida and reside predominantly on the Lower Keys of; Big Pine (5,997 acres), Big Torch, Cudjoe, Howe, Little Pine, Little Torch, Middle Torch, No Name (998 acres), Sugarloaf, and Summerland. The underlying resource that enables these particular islands to be populated is the availability of fresh water. Two thirds of the population can be observed on Big Pine and No Name Key. Areas typically used for grazing are the pinelands, hardwood hammocks, recent clearings, roadsides, and grassy areas. (The Red Book, FWS)
Status and Conservation
Presently the biggest impact on the mortality of the Key deer is the loss of habitat to development. Future population growth only increases these situations. The population is also affected by road kills, predation from dogs, and overhunting during the 1940’s and 1950’s. The Key deer has been designated as an endangered species under the Endangered Species Act of 1973, and protected under the Lacey Act. Due to efforts from local, state, and national agencies the population of Key deer is approximately 800. With an increase in population the probability of motor accidents also increase. Efforts in the future may experiment with the expanding the Key deer habitat by relocating them to other non or less populated islands with similar habitats.
References:
Conservation Management Institute Website, March 28, 2001.
Florida Environment Website, March 6, 2000.
Geist, V., and F. Walther, eds. 1974. The behavior of ungulates and its relation to management. Internat. Union Conserv. Nature and Natural Resources Publ., n.s., no. 24, 2 vols.
Geist, V., Deer of the World, Their Evolution, Behavior, and Ecology: Stackpole Books; 1st Edition: l998.
Hickman, Roberts, Larson. 1997. Integrated Principles of Zoology; pgs. 602, 607, 616, 623, 702, 705.
Prescott, Harley, Klein. 1993. Microbiology, 2nd ed. pgs. 568-571.
Putnam, R. 1988. The natural history of the deer. Comstock Publ. Assoc., Cornell Univ. Pr., Ithaca. 191 pp. QL737.U55P87 1989.
Rue III, L.L.; The Deer of North America; Outdoor Life Books, Danbury, CT. , 1989.
Smith, Robert L. 1996. Ecology and Field Biology, 5th ed. pgs. 109-112, 125-127, 179, 472.
Texas A & M Website, Key Deer Research Project.
The Ultimate Ungulate Website, April 13, 2001.
U.S. Fish and Wildlife Service 1990. Endangered and Threatened Species of the Southeastern United States (The Red Book)
U.S. Fish and Wildlife Service Website, National Key Deer Wildlife Refuge
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