Fox Squirrels Match Food Assessment and Cache Effort to Value and Scarcity

Abstract

Scatter hoarders must allocate time to assess items for caching, and to carry and bury each cache. Such decisions should be driven by economic variables, such as the value of the individual food items, the scarcity of these items, competition for food items and risk of pilferage by conspecifics. The fox squirrel, an obligate scatter-hoarder, assesses cacheable food items using two overt movements, head flicks and paw manipulations. These behaviors allow an examination of squirrel decision processes when storing food for winter survival. We measured wild squirrels' time allocations and frequencies of assessment and investment behaviors during periods of food scarcity (summer) and abundance (fall), giving the squirrels a series of 15 items (alternating five hazelnuts and five peanuts). Assessment and investment per cache increased when resource value was higher (hazelnuts) or resources were scarcer (summer), but decreased as scarcity declined (end of sessions). This is the first study to show that assessment behaviors change in response to factors that indicate daily and seasonal resource abundance, and that these factors may interact in complex ways to affect food storing decisions. Food-storing tree squirrels may be a useful and important model species to understand the complex economic decisions made under natural conditions.

Seed fate and decision‐making processes in scatter‐hoarding rodents

“…energy content) of a seed (e.g. Stapanian & Smith, ), recent evidence on several fronts suggests that hoarding behaviour is quite flexible and allows animals to adapt their valuation of seeds based on current and anticipated future conditions (Tamura et al ., ; Waite, ; Gálvez et al ., ; Cheke & Clayton, ; Delgado et al ., ; Van der Merwe, Brown & Kotler, ). As reviewed by Clayton & Emery (), De Kort et al .…”

“…Collectively, the results above suggest that scatter‐hoarders monitor the background availability of food in their environment and adjust the value that they place on additional stored reserves (see also Waite, ). Functionally, motivation may interact with food value, so that a given item is perceived as more valuable when resources are scarce (Shaner, Bowers & Macko, ; Van der Merwe, Burke & Brown, ; Delgado et al ., ; Van der Merwe et al ., ). Moreover, Eurasian jays [ Garrulus glandarius (L., 1758)] differentiate among specific types of resources and allocate those resources to storage in proportion to their scarcity (Cheke & Clayton, ).…”

“…energy content) of a seed (e.g. Stapanian & Smith, 1978), recent evidence on several fronts suggests that hoarding behaviour is quite flexible and allows animals to adapt their valuation of seeds based on current and anticipated future conditions (Tamura et al, 1999;Waite, 2001a,b;Gálvez et al, 2009;Cheke & Clayton, 2012;Delgado et al, 2014;Van der Merwe, Brown & Kotler, 2014). As reviewed by Clayton & Emery (2007), De , Grodzinski & Clayton (2010), Kamil & Gould (2008), Raby & Clayton (2010) and Pravosudov & Roth (2013), scatter-hoarding animals possess an array of cognitive abilities that allow them to assess, anticipate, and adjust to specific contexts.…”

Eastern gray squirrels are consistent shoppers of seed traits: insights from discrete choice experiments

“…Multiple seed traits influence rodent foraging decisions (Xiao & Zhang 2006;Wang et al 2012). On encountering a seed, scatter-hoarding rodents likely evaluate quality and condition (Preston & Jacobs 2009;Delgado et al 2014). Seeds germinating immediately or seeds with a lower mass are of a low storage value and tend to be consumed immediately and carried shorter distances (Smallwood et al 2001;Sundaram et al 2015).…”

How squirrels protect their caches: Location, conspicuousness during caching, and proximity to kin influence cache lifespan

“…Fox squirrels ( Sciurus niger ) use two overt behaviors to assess food items, head flicks and paw manipulations. These behaviors may help squirrels assess the quality, weight, and perishability of food items before caching or eating them (Delgado, Nicholas, Petrie, & Jacobs, 2014; Preston & Jacobs, 2009). For example, fox squirrels are significantly more likely to cache than eat items after they perform a head flick (Delgado et al, 2014; Preston & Jacobs, 2009).…”