| What is Translocation? As more animal populations decline and become endangered, wildlife managers
examine techniques to increase survival and bolster marginalized species. Today, many
species at risk of extinction are candidates for translocation. Translocation is the
removal and release of an animal from an area of high population to another where the
population is in decline. This seems like a good idea, yet translocations are costly and
successful methods are difficult to discern for each species when translocation is
employed.
Captive raising and releasing animals is another form of translocation. In some instances,
captive breeding has been the difference between recovery and extinction for animals such
as the California condor (Gymnogyps californianus) and the black-footed ferret (Mustela
nigripes). What appears to be a very straight-forward technique for getting animal
populations back where they belong is actually very complex and difficult. By looking at
only one part of the translocation process, supplemental feeding, we will see that a lot
of consideration must be made before an animal is successfully established into their new
habitat.
What is Supplemental Feeding?
As an aspect of many translocations,
biologists and game managers provide supplemental food to animals as
they enter a new habitat. This is also
referred to as “soft” releasing the animal. The purpose is to increase
survival and minimize the negative effects during translocation. Soft released animals are
contained within a shelter at the release location to allow acclimatization to the new
environment before the animal is completely responsible for its own welfare. While the
animals are housed at their release site, supplemental food is offered. The intent is to
bridge any barrier that may impede the animal from foraging naturally. Although not always
necessary, supplemental feeding is believed to be crucial to the success of the
translocation.
The Effects of Supplemental Feeding
So what happens when one starts to provide food for animals
that should be able to forage for themselves? Depending on the animal, results of
supplemental feeding can be beneficial or detrimental. In a study of translocated dormice (Muscardinus avellanarius), hard released (without
supplemental food) dormice typically failed to find sufficient forage and required
supplemental feeding to stay alive, especially when released early in the spring.
These translocated dormice failed to locate important food resources initially, even
though they otherwise exhibited behavior similar to wild dormice. On the other hand,
although initially dependant on supplemental food, the soft-release (with supplemental
food) mice gained body mass during the study and spent an increasing amount of time away
from the release site where the supplemental food was provided. This implies that the
animals were eventually successful at finding sufficient natural forage. The
advantage of
supplemental feeding is it allows the animals to get their foot in the door of their new
habitat.
The down-side of supplementation comes from all the additional effects placing
food in the wild can bring. Predators may key in on feeding areas and hunt not only
the translocated species you want to survive, but other prey species residing in the same
area. In many cases the supplemental food may have no effect at all, result in a waste of
effort and money. For large projects, this is a large negative. In a study of bald eagles,
no differences were found in brood reduction and post-hatch failing even though over 50%
of the experimental group’s diet came from supplemental food. Although food is often
considered a limiting factor for wildlife, many supplemental feeding projects have
demonstrated food may not play as an important role as other parameters. Kit foxes did
display greater survival and recruitment when food was abundant, however predator control
created significant discrepancies to confound the idea that food is a limiting survival
factor. Even though the food had the intended benefit, there were other factors that reduced the benefits of supplemental feeding.
How Does Supplemental Food Effect Behavior?
Providing forage for animals could be interpreted as a positive
reinforcement. If desirable foods are offered, then animals will develop preferences for
those foods through natural learning schemes. By changing the constraints on a group of
animals, supplemental feeding can modify the behavior for that group. For many species,
food is not only a limiting factor for survival but also a major stimulus for many of
their behaviors. One of the behaviors that researchers want to minimize is dispersal from
release areas. Dispersal typically involves exposure to unfamiliar resources and
predators, and translocated animals that do not disperse typically have greater survival.
Supplemental food often has had the desired effect of
minimizing dispersal behavior and increasing survival immediately
after release. Again,
there is a down-side. If the animal is offered a highly desirable food, and they develop a strong
preference for the food offered, the animal will take longer to reduce their dependence
on the supplemental food.
Nutritional Things to Consider
Normally, translocations are most successful when executed
in the spring when natural forage is abundant and weather conditions are relatively mild.
The animal will have less nutritional demand than during harsher weather. Likewise, there
will be more available natural forage and a greater chance that animals will reduce their
dependency on supplementation. In some cases, reintroductions are more successful when
adult animals are released rather than young. Nutritionally, this makes sense as adults
are under less pressure to grow and develop so any lag in the transition from one diet to
another will have less effect. Animals under stress stop eating. Providing a similar diet
to the one the animals are accustomed will reduce any stress a completely novel diet in
the release area may create. Further, the diet offered in captivity should not vary
greatly from the diet the animal will encounter in the wild. If differences between the
two diets are great enough, a period of time will be required for the animal’s
physiology to accommodate the new diet.
Will Supplemental Forage Help the Pygmy Rabbit?
Washington State University is attempting to return the
endangered Colombia Basin pygmy rabbit to a population state that is self-sustaining. To
figure out the best method for translocating pygmy a more robust population from Idaho
will be used to test various release methods. One method to be tested will be a soft
release. Biologists will provide food and protective shelter at the release site for a
sample of animals. The food offered will be a mixture of food they received in captivity
and food they will encounter in the wild. After the animals are allowed full access to
their new habitat, a decreasing amount of supplemental food will be offered. Hopefully,
the rabbits will move quickly to natural forage. Because these animals will not have to
begin foraging immediately upon release and will have more time to foster survival
instincts, success for soft released animals should increase. |
