Is partial acorn consumption a strategy to avoid depletion of caches during pilferage of acorns?
Cache pilferage by competing conspecifics is very common in hoarding behaviour in animals and members of rodent communities use a wide variety of strategies to minimize it. In this study, we investigated one of these strategies. We observed that some rodent species partially consume acorns leaving the embryo intact. We investigated whether this behavior in Mus spretus Lataste 1883 (Algerian mouse), was a strategy to avoid cache pilferage by competing conspecifics. Partially consumed acorn remains generated in underground stores could be seen by competing conspecifics as leftovers and rejected. They would not be consumed and therefore not stolen. To test the veracity of our hypothesis, we designed three experiments in which we studied preference for intact acorns, acorns partially consumed by the rodent itself or remains produced by other rodent competing conspecifics. We wanted to know whether the leftovers of partially consumed acorns were rejected. We verified that these remains are more highly valued than intact acorns and even the remains of the rodent’s own previous consumption, thus indicating that our hypothesis is untrue. They are not used as a strategy to avoid theft. However, preference for the remains of other rodents’ acorns could well form part of an anti-theft strategy. If they are being used as a decoy to attract the attention of thieves to prevent intact acorns from being consumed, the intact acorns would remain better preserved in the stores for a longer time. The remains were consumed before intact acorns. We verified that rodents prefer the remains of other rodents’ acorns to their own, and even to intact acorns. This behavior would form part of the strategy aimed at reducing the reserves of other rodents to avoid future competition by conspecifics.
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One species of rodent Mus spretus with 15 mice (1-15) is provided with 2 species of acorns Quercus ilex (E) and Quercus pyrenaica (R) for 10 days. We studied the preference of rodents to use acorns, acorns manufactured by the rodent itself, by a conspecific competitor or intact acorns We use 6 kinds of acorns: Intact (denoted with the letter I) that can belong to the species Q. ilex (Ii) or to Q. pyrenaica (Ip). Partially eaten by the rodent itself (denoted with the letters PI) that may belong to the species Q. ilex (PIi) or to Q. pyrenaica (PIp) and partially eaten by another conspecific competitor (denoted with the letters PO) that may belong to the species Q. ilex (POi) or to Q. pyrenaica (POp). In the first, we studied the preference of rodents to use partially consumed acorns, acorns manufactured by the rodent itself or intact acorns. We gave the fifteen rodents five intact Q. ilex acorns (Ii), five intact Q. pyrenaica acorns (Ip), five Q. ilex acorns previously partially consumed by the rodent itself (PIi), and five Q. pyrenaica acorns previously partially consumed by the rodent itself (PIp), every day for ten days. In the second experiment we present intact acorns versus remains previously consumed by other congeneric rodents. We gave five intact Q. ilex acorns (Ii), five Q. pyrenaica acorns (Ip), and five Q. ilex acorns partially consumed by a potential conspecific competitor (POi) and five Q. pyrenaica acorns partially consumed by a conspecific competitor (POp), every day In the third experiment, we gave five Q. ilex acorns partially consumed by the rodent itself (PIi), five Q. pyrenaica acorns partially consumed by the rodent itself (PIp), five Q. ilex acorns partially consumed by a competitive conspecific (POi) and five Q. pyrenaica acorns partially consumed by a competitive conspecific (POp). Each specimen had access to twenty partially consumed acorns each day (ten were their own remains (PI) and to ten belonging to other rodents (PO)).
Consejería de Educación, Junta de Castilla y León