Datasheet
Animal production (pathway cause)
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Top of page| Picture | Title | Caption | Copyright |
|---|---|---|---|
| Free-ranging goats | Free-ranging goats spreading the highly invasive shrub Prosopis juliflora, by eating the sweet pods and excreting viable seeds over a wide area. Baringo District, Kenya. | N.M. Pasiecznik | |
| A farmer showing a seeding of Prosopis juliflora | A farmer showing a seeding of Prosopis juliflora just pulled from a nearby pile of cow dung. Baringo District, Kenya. | N.M. Pasiecznik |
Identity
Top of pagePreferred Scientific Name
- Animal production (pathway cause)
International Common Names
- French: Production animal
- Portuguese: Produção animal
Local Common Names
- : Elevage
- : Livestock rearing
- Portugal: Pecuária
Overview
Top of pageFeral populations of domesticated livestock comprise some of the most invasive species in the world in terms of impact. Goats, sheep, pigs, cattle, deer and rabbits have proved devastating to local flora and fauna, especially on small islands. Control is also hampered as they often provide valuable meat for local people. Several animals introduced for fur production are also amongst the worst invasive species, including the ermine and coypu. Livestock as vectors are also a significant cause of long distance introduction (via trade in live animals) and local spread (from trade and extensive grazing) of a wide range of invasive pests and diseases, mainly animal pests and pathogens, and weed seeds.
Description
Top of pageSummary of organism types or species introduced
Domesticated animals introduced as livestock primarily for meat and milk are probably the most important group, and which became feral, including pigs (Sus scrofa), goats (Capra hircus), sheep (Ovis aries, Ovis ammon), cattle (Bos taurus), donkeys (Equus asinus), rabbits (Oryctolagus cuniculus) and various species of deer (Cervus spp.). Also important are mammals introduced for the production of fur which subsequently escaped and naturalized, including the coypu (Myocastor coypus), American mink (Mustela vison), ermine(Mustela erminea), weasel (Mustela nivalis) and ferret (Mustela furo), the latter being the domesticated form of the European pole-cat (Mustela putorius). Less significant organism types intentionally introduced internationally are birds introduced as game, and insects for honey production or as pollinators, most notably the Africanized honeybee (Apis mellifera scutellata) and various Bombus spp.
Where livestock act as a vector, two main organism types are transported. The main groups include almost all animal pests and pathogens, and most are known to be carried by this means (see the Animal Health and Production Compendium (http://www.cabi.org/ahpc/) and OIE websites (http://www.oie.int/) for comprehensive lists and information on each). Invasive plants are the other main organism type introduced and spread by livestock as vectors, either internally or externally. Forage plants have also been introduced intentionally to feed livestock, or accidentally as fodder accompanying live animal movements.
Principle processes
Five principle process of invasive species movement through animal production have been identified, separated also by the main organism types as identified above.
(1) The introduction of animals, and either intentional release or accidental escape.
(2) The accidental introduction of animal pests and pathogens using livestock as the vector.
(3) The accidental introduction of weeds (internally or externally) using livestock as the vector.
(4) The accidental introduction of weeds as seeds, using stored fodder as the commodity.
(5) The intentional introduction of forage plants, followed by escape from cultivation.
The animals themselves and their diseases can be both internationally introduced and locally dispersed by animal production. However, the movement of weed seeds, either via digestion/excretion, or via seeds stuck to wool or mud, etc., is much more likely to involve short-distance dispersal rather than international introduction, though there are rare cases where weed seeds are carried in the gut and passed out on arrival at a new destination, or weed seeds are carried in the wool or fur of transported animals, or in mud stuck to their hooves or other body parts.
Note, the term ‘animals’ is mainly used to describe mammals, though birds and insects are included. Bees are also known to be vectors, for example, and their movement has been attributed to the introduction of the varroa mite (Varroa destructor), a major pest of bee colonies.
Human-mediated history
There is long history of the movement of domesticated animals around the world, beginning with the Egyptians bring domesticated goats from the Middle East to Africa some 10,000 years ago. The arrival of extensively grazed herds of small ruminants is likely to have had effects on local vegetation even then. Thus, early routes followed the introduction of the first domesticated animals. However, the first significant negative impacts to be recorded from feral populations were after sailors had left goats, pigs and other animals on isolated oceanic islands during their travels, as a source of food on return or subsequent journeys. Left to themselves, they were highly destructive, and many endemic island species are likely to have become extinct even before any formal scientific records were made of them. Increased trade in live animals in recent history has allowed the sometimes rapid and certainly global spread of a number of livestock pests and pathogens, and also weeds, which continues to this day.
Species Transported by Cause
Top of pageManagement
Top of pageReducing the risks of introduction is the principle means of preventing further invasions resulting from this pathway, which requires improved quarantine controls regarding the movement of live domesticated livestock (McClelland, 2001). As islands appear to be at particular risk, it would appear prudent to not allow any further importation of live animals, for the pests they may vector, or with them becoming invasive themselves (see for example, papers in Veitch and Clout, 2001).
Concerning the management and eradication of feral animal populations once introduced, numerous methods have been attempted. They have proved successful on islands when further in-migration can be prevented. The main control methods involve culling and baiting, and use hunters with guns and/or traps, and poisons. Some examples include the eradication of pigs (Schuyler et al., 2001), goats (Parkes et al., 2001), sheep (Klinger et al., 2001), goats and pigs (Kessler, 2001), goats and rabbits (Bullock et al., 2001; Burbidge and Morris, 2001), and rabbits and other rodents (Merton et al., 2001; Micol and Jouventin, 2001; Torr, 2001).
Other papers in Veitch and Clout (2001) also describe examples of attempts to eradicate animal pests and pathogens, and environmental weeds from island ecosystems.
However, the central issue remains the same – live animal imports always carry some risk, and the only means to reduce risks to zero is to prevent all live imports. Stringent quarantine requirements is next best, and if conducted rigorously and conscientiously by well trained staff, can be very effective.