Acorn Harvesting by Florida Scrub Jays

Abstract

We documented number of acorns eaten, cached, and retrieved by Florida Scrub Jays (Aphelocoma coerulescens coerulescens), through one full annual cycle and part of another, in an oak scrub habitat characterized by abundant and reliable annual acorn crops. Jays consumed acorns during all months, with highest consumption from September through February and lowest in June and July. From August through December, most acorns consumed by jays were picked directly from shrubs; during the remaining 7 mo, acorns were recovered from ground stores. Acorn caching occurred throughout the fall, peaking in September and October. Data pooled across sex and age classes suggest that individual jays, on average, each cached between 6500 and 8000 acorns during fall of 1974. Only about one—third of those acorns were recovered later. Intact acorns recovered by Scrub Jays during fall usually were reburied, but by summer most recovered acorns were consumed. Acorn crops in the study area exhibit moderate annual variation but no crop failures. Acorns are available in substantial numbers every year, permitting Florida Scrub Jay territories to serve without fail as year—round warehouses of stored acorns. Those stores provide resources to carry group members through seasons of low arthropod availability, and perhaps facilitate delayed dispersal by juveniles. Use of a habitat characterized by relatively large and dependable annual acorn crops that are evenly dispersed, coupled with caching behavior, may contribute to the maintenance of permanent territoriality and cooperative breeding in this population.

Evidence for cache surveillance by a scatter-hoarding rodent

“…Cache revisiting is a hypothesized mechanism by which scatterhoarding animals enhance their memory to remember locations over long periods (DeGange et al 1989;Brodin 1992;Grubb & Pravosudov 1994;Roth et al 2012). We found that Central American agoutis in Panama regularly inspected their caches, which supports a key assumption of the memory enhancement hypothesis.…”

“…Eavesdropping thieves may represent a real cost of cache surveillance in this system. The cache revisiting and inspection behaviours observed in this study are fully consistent with the predictions of the memory enhancement hypothesis (DeGange et al 1989;Brodin 1992;Grubb & Pravosudov 1994;Roth et al 2010), yet they do not conclusively demonstrate that cache surveillance actually serves to strengthen spatial memory. Experimental confirmation is needed to determine whether agouti cache surveillance increases long-term spatial memory and is a mechanism facilitating the ability of agoutis to remember cache locations 120 days after burial.…”

Food storage in a changing world: implications of climate change for food-caching species

“…Long-term cachers store food as a response to a certain lack of food in the future. Species in this class typically engage in intense periods of caching, usually in the late summer or fall [31,66,154,164] and are followed by intervals of limited resources (e.g. winter) during which caches are retrieved.…”

The Relevance of Burial to Evade Acorn Predation in an Oak Forest Affected by Habitat Loss and Land Use Changes

“…As mentioned above, Peromyscus mice would be the main nocturnal consumer of acorns and, therefore, Aphelocoma birds would be the main diurnal consumer of exposed acorns. Birds are important acorn consumers in oak forest of North America (DeGange et al, 1989), but this group of foragers would be the second main guild of acorn removers, after rodents, in European oak forest (Perea et al, 2012). In our case, Aphelocoma birds seems to be important acorn removers in different habitat types of the fragmented forest under study, which is probably linked to their ability to move across the landscape.…”

“…In our case, Aphelocoma birds seems to be important acorn removers in different habitat types of the fragmented forest under study, which is probably linked to their ability to move across the landscape. Indeed, because these birds were suggested to be effective long-distance seed dispersers (DeGange et al, 1989), they are likely to move acorns from forest patches towards human-impacted habitats. Nevertheless, the importance of mice and birds as acorns disperser across the different habitat types of this fragmented landscape would require more detailed studies.…”