December 28, 2007

Predation, scavenging pestering beef cattle operations

Predation and scavenging are one of the two big problems for cattle operations in the US. However, the presence of predators does not necessarily mean that predation is taking place but cattle that die of causes other than predation may be scavenged, providing meals for animals of predator species for up to several days at a time. Thus, tracks, faeces, feathers, or hair found at the site may provide evidence of animal presence at the scene but yet not of predation.

The more time that passes after a predator attack, the more difficult it becomes to determine the cause of the resulting cattle injuries or deaths. Carcass decomposition can be rapid in warm weather and destroys predation evidence. In only a few hours, scavenging birds and mammals can eliminate evidence of a predator attack.

When the cause of livestock loss cannot be readily determined, assistance may be necessary. Necropsy of a livestock carcass can be a useful tool if predators contributed to the loss. Changes in cattle behaviour can also help in determining if predators are responsible for livestock losses. Cattle behaviour in herds which are chased or attacked repeatedly by predators becomes more alert and defensive. This abnormal behavior should be readily apparent to the skilled and observant herdsperson.

The Texas Agricultural Extension Service issued a producer resource titled "Procedures for Evaluating Predation on Livestock and Wildlife". This publication suggests that in identifying predation as a cause of livestock loss, the following information may needed: 1) predator species present in the area , 2) habits and signs of  each predator species, 3) history of depredation problems in the area, 4) normal and abnormal livestock appearance and behaviour, and 5) common causes of livestock losses other than predators.

Cattle farmers should examine injured animals for the type and extent of wounds and feeding. If possible, determine whether wounds were made by mammals (canine teeth and/or claws), birds (talons and/or beaks), or other causes. Most predators tend to attack the head and neck and this is particularly true of dogs. When prey is small relative to the predator, a single bite is often adequate to kill. Predators smaller than their prey are the most likely cause of death when many bite punctures accompanied by hemorrhage are detected. Likewise, young, inexperienced predators are apt to inflict multiple injuries by random attacks without killing their prey.

A scavenging animal may not become a "calf-killer", but as the predator matures, it may be more prone to cause problems for the cattle producer. Coyotes are an example of a predator species that hones its predatory behaviour over time. Observations of wildlife specialists in the Texas High Plains indicated that 3-year old and older coyotes are primarily responsible for effective cattle attacks. Inexperienced, younger coyotes and free-ranging dogs instead leave behind bobbed tails and calf mutilation associated with inept, rear-end attacks. Dogs, on the other hand, often cause extensive injuries to young and small livestock without killing them but do not typically feed on them. Bobbed ears and tails are telltale signs of dog attacks. However, some dogs learn to kill efficiently and feed. In these cases, dogs like coyotes tend to leave torn, ragged tissue and splintered bones.

Where predation is suspected or confirmed, locate the attack, kill, and feeding sites if possible. Take detailed photographs of these sites as they may be very valuable in investigating the incident. Animals that are killed are seldom found lying in a natural position. When searching for the attack, kill, and feeding sites, consider that many predators move their kills. Additionally, scavengers may disrupt the position of a carcass. Always take proper precautions to prevent exposure during examination of animal carcasses as humans are susceptible to many diseases carried by animals. Examine carcasses for wounds, bruises, hemorrhage, broken bones and feeding. Consider necropsy as an option to gather more information on the cause of death and to help rule out different mortality factors.