Grey Squirrel Food Preferences: The Effects of Tannin and Fat Concentration

Smallwood, Peter D.; Peters, Wm. David

doi:10.2307/1938515

Cited by 127 publications

(103 citation statements)

References 27 publications

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“…germinate in the spring), whereas white oak (WO: section Quercus) acorns usually have lower tannins, lower fat content and lack winter dormancy (i.e. germinate in the autumn) (Smallwood & Peters 1986). A variety of studies have reported that Eastern gray squirrels and other animals consistently scatter hoard RO acorns in preference to WO acorns, which they are more likely to eat (e.g.…”

Section: The Handling Costs Hypothesismentioning

confidence: 99%

“…Despite the fact that these two nut species occur in different genera, they have similar compositions (nutritional content) and size but Q. variabilis acorns have approximately 20 times higher tannin content. High tannin levels act as a cue for scatter hoarding (Smallwood & Peters 1986;Hadj-Chikh et al 1996;Xiao et al 2008; but see Xiao et al 2006a,b).…”

Section: The Handling Costs Hypothesismentioning

confidence: 99%

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How plants manipulate the scatter-hoarding behaviour of seed-dispersing animals

Wall

2010

Phil. Trans. R. Soc. B

258

259

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Some plants that are dispersed by scatter-hoarding animals appear to have evolved the ability to manipulate the behaviour of those animals to increase the likelihood that seeds and nuts will be stored and that a portion of those items will not be recovered. Plants have achieved this in at least four ways. First, by producing large, nutritious seeds and nuts that are attractive to animals and that stimulate hoarding behaviour. Second, by imposing handling costs that cause animals to hoard rather than to eat items immediately. These handling costs can take one of two forms: physical barriers (e.g. hard seed coats) that take time to remove and secondary chemicals (e.g. tannins) that impose metabolic costs. Third, by masting, where a population of plants synchronizes reproductive effort, producing large nut crops at intervals of several years. Mast crops not only satiate seed predators, but also increase the amount of seed dispersal because scatter-hoarding animals are not easily satiated during caching (causing animals to store more food than they can consume) but are satiated during cache recovery. And fourth, by producing seeds that do not emit strong odours so that buried seeds are less likely to be discovered. These, and perhaps other, traits have increased the relative success of plant species with seeds dispersed by scatter-hoarding animals.

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Section: The Handling Costs Hypothesismentioning

confidence: 99%

Section: The Handling Costs Hypothesismentioning

confidence: 99%

How plants manipulate the scatter-hoarding behaviour of seed-dispersing animals

Wall

2010

Phil. Trans. R. Soc. B

258

259

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“…As the acorns selected by Mexican jays are most abundant in low elevation landscape units, the co-adapted symbiotic relationship may provide a dispersal mechanism for oak encroachment into low elevation savannas and semi-arid grasslands. Tannin contents were not measured in this study; however, red oak (e.g., Quercus emoryi) acorns reportedly have high tannin contents relative to acorns from other oaks (Smallwood and Peters 1986;Weckerly et al 1989).…”

Section: Acorn Selectionmentioning

confidence: 73%

“…Bossema (1979) proposed that a co-adapted symbiotic relationship exists between jays and oaks whereby foraging jays select ripe acorns to consume or cache, then disperse many of these acorns into sites favorable for oak recruitment. Other authors have suggested that low tannin content is the primary determinant in acorn selection by many seed predators (Smallwood and Peters 1986;Koenig and Heck 1988;Weckerly et al 1989;Johnson et al 1993;Steele et al 1993). Foraging mechanisms which minimize consumption of acorn tannins (e.g., limiting consumption to acorn portions or species with relatively low tannin content) have been observed in a variety of species (e.g., Smallwood and Peters 1986;Steele et al 1993).…”

Section: Introductionmentioning

confidence: 98%

Acorn selection by Mexican jays: a test of a tri-trophic symbiotic relationship hypothesis

Hubbard

McPherson

1997

Oecologia

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By caching acorns, jays serve as important dispersal agents for oak (Quercus) species. Yet little is known about which acorn characteristics affect selection by jays. In the traditional model of jay/oak symbiosis, large, brown, ripe acorns free of invertebrate parasites (e.g., Curculio acorn weevils) are selected by jays. Recently, it has been suggested that a tri-trophic relationship between oaks, jays, and weevils may have evolved to counter the negative dietary effects of acorn tannins. Under the tri-trophic model, jays would preferentially select acorns containing weevil larvae. We tested the assumptions that (1) acorns containing curculionid larvae exist in sufficient quantities to support jay populations and (2) jays can detect, and preferentially select, acorns containing weevil larvae, and investigated the cues by which jays select acorns. Captive Mexican jays (Aphelocomaultramarina) were presented Emory oak (Quercusemoryi) acorns in aviary feeding trials. Large, dense, viable acorns free of curculionid larvae were preferentially selected. Contrary to results of previous research, color did not affect selection. Acorn viability increased and curculionid larval occupancy decreased in adjacent savannas and isolated stands relative to existing oak woodland, perhaps favoring oak recruitment into adjacent lower-elevation grasslands. Our results compel us to reject the tri-trophic model for this system, and are consistent with the traditional jay/oak symbiosis model. Relatively long-distance dispersal of viable acorns favors Emory oak replacement, and spatial patterns of acorn viability and curculionid parasitism suggest expansion of Emory oak into adjacent low-elevation semi-arid grasslands.

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“…Rather, it reinforces that it is more profitable to transport and scatter hoard larger nuts. Other factors that would influence the choice to cache seeds include food perishability (Smallwood and Peters 1986) and increased handling time resulting in increased risk of predation (Hadj-Chikh et al 1996). However, it is possible that the prior exposure by the woylies to sandalwood seed influenced their seed preference, and because they were reared in captivity they may have developed different foraging skills to wild-raised animals.…”

Section: Discussionmentioning

confidence: 99%

When losing your nuts increases your reproductive success: sandalwood (Santalum spicatum) nut caching by the woylie (Bettongia penicillata)

Murphy

Howard

Hardy

et al. 2015

Pac. Conserv. Biol.

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To regenerate sandalwood (Santalum spicatum) stands in south-western Australia it is necessary to understand the complex relationship between woylies (Bettongia penicillata ogilbyi) and sandalwood.Sandalwood requires a seed disperser for successful recruitment and in the past the critically endangered woylie played an important role in dispersing and caching seeds, but it is not clear whether this mutualistic and antagonistic relationship is beneficial to regeneration efforts. An enclosure in a woodland and 46 Scandium-labelled seeds, enabled study of the in situ predation of seeds, caching, the fate of cached seeds, the detection of cached seeds and predation of germinated seeds. Woylies preferentially cached sandalwood, then S. acuminatum seeds, before any interest was shown in Acacia acuminata and Gastrolobium microcarpum seeds, which were virtually all eaten in situ. Of a further 500 radiolabelled and individually numbered sandalwood seeds deployed, 42.2% were eaten in situ, 20.8% had an unknown fate and 37% were cached, with some seeds being recached up to four times. After nine months, only four cached seeds remained undisturbed. Olfaction appeared to be the primary method of cache detection. To examine the recruitment rate of cached seeds, the fate of 89 transplanted sandalwood seedlings at two study sites was followed. After one month 38% were intact and growing, but half of the transplanted seedlings were dug up and the remaining endosperm was eaten in situ or taken away. The results highlight the potential of providing seed supplies, including sandalwood seeds and seeds of their hosts, to seed-dispersal marsupials for passive ecosystem repair.

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Grey Squirrel Food Preferences: The Effects of Tannin and Fat Concentration

Cited by 127 publications

References 27 publications

How plants manipulate the scatter-hoarding behaviour of seed-dispersing animals

How plants manipulate the scatter-hoarding behaviour of seed-dispersing animals

Acorn selection by Mexican jays: a test of a tri-trophic symbiotic relationship hypothesis

When losing your nuts increases your reproductive success: sandalwood (Santalum spicatum) nut caching by the woylie (Bettongia penicillata)

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