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Reproductive timing and reliance on hoarded capital resources by lactating red squirrels.

Abstract：

:Successful reproduction in a seasonal environment can be accomplished with resources that are stored before use ("capital resources") or resources that are used immediately ("income resources"). Research examining capital versus income resource usage during reproduction has primarily focused on assigning species to positions along a capital-income gradient. Here, we examine the causes and reproductive consequences of among and within-year variation in hoarded capital versus income resource usage by female North American red squirrels (Tamiasciurus hudsonicus) during mid-lactation in a highly seasonal environment. Among years, the proportion of feeding events that were on capital resources (PROPCAP) averaged 39 % during the yearly median mid-lactation periods, but ranged widely between 2 and 100 %. In years with earlier parturition dates, females primarily used hoarded capital resources during mid-lactation, whereas in years with later parturition dates, females primarily used income resources during mid-lactation. Within years, PROPCAP during mid-lactation tended to be greater in early-breeding females than in late-breeding females. Rates of water flux in females during mid-lactation provided further evidence that late-breeding females used more water-rich income resources. The proportion of litters that were partially or completely lost, and the litter mass that lactating females supported, was not influenced by the large among-year differences in hoarded capital resource usage. Red squirrels appear to delay reproduction following years with low cone production to time peak reproductive demands to be late enough to be supported by income resources that only become available later in the season. In conclusion, our results offer a rare example of the capacity of a food-hoarding mammal to support reproduction exploiting a wide range of capital and income resources.

journal_name

Oecologia

journal_title

Oecologia

authors

Fletcher QE,Landry-Cuerrier M,Boutin S,McAdam AG,Speakman JR,Humphries MM

doi

10.1007/s00442-013-2699-3

subject

Has Abstract

pub_date

2013-12-01 00:00:00

pages

1203-15

issue

eissn

0029-8549

issn

1432-1939

journal_volume

173

pub_type

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Reproductive timing and reliance on hoarded capital resources by lactating red squirrels.