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Hoarding or caching in animal behavior is the storage of food in locations hidden from the sight of both conspecifics (animals of the same or closely related species) and members of other species.Vander Wall, Stephen B. (1990) Food Hoarding in Animals. University of Chicago Press. Most commonly, the function of hoarding or caching is to store food in times of surplus for times when food is less plentiful. However, there is evidence that a certain amount of caching or hoarding is actually undertaken with the aim of ripening the food so stored, and this practice is thus referred to as ‘ripening caching’. The term hoarding is most typically used for
rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...
s, whereas caching is more commonly used in reference to
bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
s, but the behaviors in both animal groups are quite similar. Hoarding is done either on a long-term basiscached on a seasonal cycle, with food to be consumed months down the lineor 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
rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...
s such as
hamster Hamsters are rodents (order Rodentia) belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera. They have become established as popular small pets. The best-known species of hamster is the golden or Syrian ...
s and
squirrel Squirrels are members of the family Sciuridae (), a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrel ...
s, and many different
bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
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 In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the p ...
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. This phenomenon is referenced in the fable
The Ant and the Grasshopper The Ant and the Grasshopper, alternatively titled The Grasshopper and the Ant (or Ants), is one of Aesop's Fables, numbered 373 in the Perry Index. The fable describes how a hungry grasshopper begs for food from an ant when winter comes and is ...
. 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, tayras (a Central American weasel) have been observed to harvest whole green plantains, hide them, and then come back to eat them after they have ripened. Leafcutter ants harvest pieces of inedible leaves and then cache them in underground chambers to ripen with a fungus which is the main food for the colony. Contrary to popular belief, there is no scientific evidence that crocodilians such as the American Alligator cache large prey underwater to consume later.


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 The fox squirrel (''Sciurus niger''), also known as the eastern fox squirrel or Bryant's fox squirrel, is the largest species of tree squirrel native to North America. It is sometimes mistaken for the American red squirrel or eastern gray squirr ...
, and wood mouse. Specifically, those who do not migrate to warmer climates or hibernate for winter are most likely to scatter hoard. This behavior plays an important part in
seed dispersal In spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...
, as those seeds that are left uneaten will have a chance to
germinate Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an flowering plant, angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the sp ...
, thus enabling plants to spread their
population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...
s 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. 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 pilferage. However, having multiple cache sites is costly because it requires a good spatial memory. Scatter-hoarders generally have larger hippocampi than animals that do not participate in scatter-hoarding behavior. Additionally, studies have shown that hippocampal volume in scatter-hoarders varies seasonally and based on the harshness of the climate that the animal lives in. In larder hoarding, the hoard is large and is found in a single place termed a
larder A larder is a cool area for storing food prior to use. Originally, it was where raw meat was larded—covered in fat—to be preserved. This method slowed spoilage by sealing out air, bacteria, and moisture. In colder larders (4°C/40°F or lower) ...
, which usually also serves as the nest where the animal lives.
Hamster Hamsters are rodents (order Rodentia) belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera. They have become established as popular small pets. The best-known species of hamster is the golden or Syrian ...
s are famous larder hoarders. Indeed, the German verb "hamstern" (to hoard) is derived from the noun "Hamster" which refers to the rodent; similar verbs are found in various related languages ( Dutch ''hamsteren'', and Swedish ''hamstra''). Other languages also draw a clear connection between hamsters and hoarding: Polish ''chomikować'', from ''chomik'' – hamster;
Hebrew Hebrew (; ''ʿÎbrit'') is a Northwest Semitic languages, Northwest Semitic language within the Afroasiatic languages, Afroasiatic language family. A regional dialect of the Canaanite languages, it was natively spoken by the Israelites and ...
''hamster''; ''oger'' (אוגר) comes from ''to hoard''; ''le'egor'' (לאגור). A disadvantage of larder hoarding is that if a cache is raided, this is far more problematic for the animal than if it were a scatter hoarder. While the hoard is much easier to remember the location of, these larger hoards must also be more staunchly defended.


Related behaviors


Guarding

Most species are particularly wary of onlooking individuals during caching and ensure that the cache locations are secret. Not all caches are concealed however, for example shrikes store prey items on thorns on branches in the open.


Shared or individual hoarding

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. There are only two species in which kin selection has resulted in a shared food store, i.e. beavers (''Castor canadensis'') and acorn woodpeckers (''Melanerpes formicivorous''); the former live in family groups and construct winter larders of submerged branches, while the latter are unusual in that they construct a conspicuous communal larder.
Wolves The wolf (''Canis lupus''; : wolves), also known as the grey wolf or gray wolf, is a canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, including the dog and dingo, though gr ...
,
foxes Foxes are small-to-medium-sized omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull; upright, triangular ears; a pointed, slightly upturned snout; and a long, bushy tail ("brush"). Twelve species ...
, and coyotes identify their food caches by
scent-marking In ethology, territory is the sociographical area that an animal consistently defends against conspecificity, conspecific competition (biology), competition (or, occasionally, against animals of other species) using agonistic behaviors or (less ...
them, usually after they have been emptied.


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 suggested the value of cached food is equal to the hoarder's ability to retrieve it.


Reciprocal pilfering

It has been observed that members of certain species, such as
rodents Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...
and chickadees, act as both hoarder and pilferer. In other words, pilfering can be reciprocal and, thus, tolerable.


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. These results, and those from other studies, demonstrate the dynamic nature of the food supplies of scatter hoarding animals.


Deception

Group-foraging
common raven The common raven or northern raven (''Corvus corax'') is a large all-black passerine bird. It is the most widely distributed of all Corvidae, corvids, found across the Northern Hemisphere. There are 11 accepted subspecies with little variatio ...
s, (''Corvus corax''), scatter hoard their food and also raid the caches made by others. Cachers withdraw from conspecifics when hiding their food and most often place their caches behind structures, obstructing the view of potential observers. Raiders watch inconspicuously and keep at a distance to cachers close to their cache sites. In response to the presence of potential raiders or because of their initial movements towards caches, the cachers frequently interrupt caching, change cache sites, or recover their food items. These behaviors suggest that ravens are capable of withholding information about their intentions, which may qualify as tactical deception. Similarly,
Eurasian jay The Eurasian jay (''Garrulus glandarius'') is a species of passerine bird in the crow family Corvidae. It has pinkish brown plumage with a black stripe on each side of a whitish throat, a bright blue panel on the upper wing and a black tail. The ...
s (''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.


See also

* Food storage


References


Further reading

*


External links


TerraNaturalist channel on YouTube
Video shows several bird species and caching behavior. {{Ethology Ethology Eating behaviors Birds Animals by adaptation