Cervids are an important food source for many predators throughout their geographic range. For example, one study showed that over 80% of the feces of gray wolves in Algonquin Park in Canada contained the remains of white-tailed deer. Cervids are host to a variety of endoparasites, including parasitic flatworms (Cestoda and Trematoda) and many species of roundworm (Nematoda) spend at least part of their lifecycle in the tissues of cervid hosts. Cervids are also vulnerable to various forms of parasitic arthropods including ticks (Ixodoidea), lice (Phthiraptera), mites (Psoroptes and Sarcoptes), keds (Hippoboscidae), fleas (Siphonaptera), mosquitoes (Culicidae), and flies (Diptera). In addition, cervids compete with other species for food and other resources, which can effectually limit both inter- and intraspecific population growth.
Cervids play an integral role in the structure and function of the ecosystems in which they reside, and some species have been shown to alter the density and composition of local plant communities. For example, on Isle Royale National Park, MI, moose (Alces alces) have been shown to alter the density and composition of foraged aquatic plant communities, and fecal nitrogen transferred from aquatic to terrestrial habitats via the ingestion of aquatic macrophytes increases terrestrial nitrogen availability in summer core areas. Foraging by cervids has been shown to have a significant impact on plant succession, and plant diversity is greater in areas subjected to foraging. As a result, foraging might lead to shifts from one plant community type to another (e.g., hardwoods to conifers). In addition, moderate levels of foraging by cervids may increase habitat suitability for conspecifics. For example, litter from foraged plants decomposes more quickly than non-browsed, thus increasing nutrient availability to the surrounding plant community. Moreover, nutrient inputs from urine and feces have been shown to contribute to longer stem growth and larger leaves in the surrounding plant community, which are preferentially fed upon during subsequent foraging bouts. Finally, research has shown that the decomposition of cervid carcasses can result in elevated soil macronutrients and leaf nitrogen for a minimum of two years.
Although cervids can be host to numerous species of pathogenic bacteria and protozoa, in conjunction with anaerobic fungi, similar classes of microorganisms are one of the major reasons that cervids are as abundant and diverse as they are today. Bacteria comprise between 60 and 90% of the microbial community present in the ruminant's gastrointestinal (GI) tract and help break down cellulose. Ciliated protozoa, which makes up 10 to 40% of the microbe community within the rumen, help break down cellulose, while also feeding on starches, proteins and bacteria. The presence of anaerobic fungi in the rumen has only been known since the early 1970's. These fungi make up between 5 to 10% of the rumen's microbial abundance and are thought to help break down the cell wall of ingested plant material. Bacteria and protozoa that pass from the upper to the lower regions of the GI tract represent a significant portion of the dietary nitrogen required by their host.
Ecosystem Impact: disperses seeds
- rumen bacteria, (Selenomonads)
- rumen bacteria, (Oscillospira)
- rumen protozoa, (Entodinium)
- rumen protozoa, (Dasytricha)
- rumen protozoa, (Diplodinia)
- rumen protozoa, (Isotricha)
- rumen protozoa, (Epidinia)
- rumen fungi, (Neocallimastix)
- rumen fungi, (Caecomyces)
- rumen fungi, (Pyromyces)
- rumen fungi, (Orpinomyces)