Hoarding (animal behavior)
Hoarding or caching in
Hoarding is done either on a long-term basis—cached on a seasonal cycle, with food to be consumed months down the line—or on a short-term basis, in which case the food will be consumed over a period of one or several days.
Some common animals that cache their food are rodents such as hamsters and squirrels, and many different bird species, such as rooks and woodpeckers. The western scrub jay is noted for its particular skill at caching. There are two types of caching behavior: larder hoarding, where a species creates a few large caches which it often defends, and scatter hoarding, where a species will create multiple caches, often with each individual food item stored in a unique place. Both types of caching have their advantage.
Function
Caching behavior is typically a way to save excess edible food for later consumption—either soon to be eaten food, such as when a jaguar hangs partially eaten prey from a tree to be eaten within a few days, or long term, where the food is hidden and retrieved many months later. Caching is a common adaptation to seasonal changes in food availability. In regions where winters are harsh, food availability typically becomes low, and caching food during the times of high food availability in the warmer months provides a significant survival advantage. For species that hoard perishable food weather can significantly affect the accumulation, use and rotting of the stored food.[3] This phenomenon is referenced in the fable The Ant and the Grasshopper.
However, in ripening caching behavior, animals collect and cache food which is immediately inedible but will become "ripe" and edible after a short while. For instance,
Hoard distribution and size
Scatter hoarding is the formation of a large number of small hoards. This behavior is present in both birds (especially the Canada jay) and small mammals, mainly squirrels and other rodents, such as the eastern gray squirrel, fox squirrel, and wood mouse. Specifically, those who do not migrate to warmer climates or hibernate for winter are most likely to scatter hoard.[5][6][7] This behavior plays an important part in seed dispersal, as those seeds that are left uneaten will have a chance to germinate, thus enabling plants to spread their populations effectively. While it is clear why some animals scatter their food caches, there is still the question of why they would store the food outside of their bodies in the first place. The reason for this is that scatter hoarders must remain active during the caching period in order to hide the most food in the most places possible. Storing the food inside their body would reduce their mobility and be counterproductive to this objective.[8]
Cache spacing is the primary technique that scatter hoarders use to protect food from pilferers. By spreading the food supply around geographically, hoarders discourage competitors who happen upon a cache from conducting area-restricted searching for more of the supply. Despite cache spacing, hoarders are still unable to eliminate the threat of
In larder hoarding, the hoard is large and is found in a single place termed a
Related behaviors
Guarding
Most species are particularly wary of onlooking individuals during caching and ensure that the cache locations are
Although a small handful of species share food stores, food hoarding is a solo endeavor for most species, including almost all rodents and birds. For example, a number of jays live in large family groups, but they don't demonstrate sharing of cached food. Rather, they hoard their food supply selfishly, caching and retrieving the supply in secret.[17]
There are only two species in which kin selection has resulted in a shared food store, i.e.
Pilfering
Pilferage occurs when one animal takes food from another animal's larder. Some species experience high levels of cache pilferage, up to 30% of the supply per day. Models of scatter hoarding[19][20][21] suggested the value of cached food is equal to the hoarder's ability to retrieve it.[22]
Reciprocal pilfering
It has been observed that members of certain species, such as
Recaching
Animals recache the food that they've pilfered from other animal's caches. For example, 75% percent of mildly radioactive (thus traceable) Jeffrey pine seeds cached by yellow pine chipmunks were found in two cache sites, 29% of the seeds were found in three sites, 9.4% were found in four sites and 1.3% were found in five sites over a 3-month period.[23] These results, and those from other studies, demonstrate the dynamic nature of the food supplies of scatter hoarding animals.
Deception
Group-foraging
Similarly, Eurasian jays (Garrulus glandarius) when being watched by another jay, prefer to cache food behind an opaque barrier rather than a transparent barrier, suggesting they may opt to cache in out-of-view locations to reduce the likelihood of other jays pilfering their caches.[25]
See also
References
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- ^ Hampton, R. R. & Sherry, D. F. (1994) The effects of cache loss on choice of cache sites in the black-capped chickadee. Behav. Ecol. 5:44-50
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- ^ Heinrich, B. & Pepper, J. W. (1998) Influence of competitors on caching behavior in the common raven, Corvus corax. Anim. Behav. 56:1083-1090
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- ^ Waite, T.A., (1992). Gray jay scatterhoarding behavior, rate maximization and the effect of local cache density. Ornis. Scand., 23: 175-182
- ^ Koenig, W.D. and Mumme, R.L., (1987). Population Ecology of the Cooperatively Breeding Acorn Woodpecker. Princeton, New Jersey. Princeton University Press. 0691084645
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Further reading
- Jenkins, Stewart H.; Breck, Stewart W. (November 1998). "Differences in Food Hoarding Among Six Species of Heteromyid Rodents". JSTOR 1383013.
External links
- TerraNaturalist channel on YouTube Video shows several bird species and caching behavior.