Flexible parents: joint effects of handicapping and brood size manipulation on female parental care inNicrophorus vespilloides

Abstract

Parental care is highly variable, reflecting that parents make flexible decisions in response to variation in the cost of care to themselves and the benefit to their offspring. Much of the evidence that parents respond to such variation derives from handicapping and brood size manipulations, the separate effects of which are well understood. However, little is known about their joint effects. Here, we fill this gap by conducting a joint handicapping and brood size manipulation in the burying beetle Nicrophorus vespilloides. We handicapped half of the females by attaching a lead weight to their pronotum, leaving the remaining females as controls. We also manipulated brood size by providing each female with 5, 20 or 40 larvae. In contrast to what we predicted, handicapped females spent more time provisioning food than controls. We also found that handicapped females spent more time consuming carrion. Furthermore, handicapped females spent a similar amount of time consuming carrion regardless of brood size, whereas controls spent more time consuming carrion as brood increased. Females spent more time provisioning food towards larger broods, and females were more likely to engage in carrion consumption when caring for larger broods. We conclude that females respond to both handicapping and brood size manipulations, but these responses are largely independent of each other. Overall, our results suggest that handicapping might lead to a higher investment into current reproduction and that it might be associated with compensatory responses that negate the detrimental impact of higher cost of care in handicapped parents.

Resource allocation is determined by both parents and offspring in a burying beetle

“…Evidence from studies on N. vespilloides also suggests that parents respond to cues other than begging when determining the amount of provisioning, as the parents provision more food to inbred offspring, although the same offspring also beg less than their outbred counterparts (Mattey, Richardson, Ratz, & Smiseth, 2018). Similarly, adult N. vespilloides are known to adjust their behaviour to the number of larvae in a brood (Ratz & Smiseth, 2018; Smiseth & Moore, 2007). In our study, the older larvae of the mid‐aged and old treatments may have been assessed as being of good quality, potentially due to their size or associated traits, thereby prompting the female into elevating the amount of care beyond the level provided by control females.…”

Biparental negotiation or larval begging? Determinant of male provisioning in a burying beetle (Nicrophorus quadripunctatus)

“…Female burying beetles will sometimes adjust provisioning in response to mate removal (Fetherston et al, 1994) but sometimes do not (Rauter & Moore, 2004;Smiseth et al, 2005). More recently, handicapping by the attachment of lead weights to one parent has been used to study negotiation (Suzuki & Nagano, 2009;Creighton et al, 2015;Suzuki, 2016;Ratz & Smiseth, 2018). Other studies have examined the effect of larval begging on parental provisioning.…”

Parental responses to increasing levels of handicapping in a burying beetle

“…Wright and Cuthill 1989;Harrison et al 2009), confirming that parents plastically reduce the amount of care they provide when the cost of care increases. However, a recent study on the burying beetle Nicrophorus vespilloides found that handicapped females provided more care than control females (Ratz and Smiseth 2018). This finding contradicts the implicit assumption that handicapping simply increases the cost of care.…”

“…Parental care encompasses any parental trait that enhances the survival and/or growth of a parent's offspring, often at a cost to the parent's ability to invest in other current or future offspring (Clutton-Brock 1991;Royle et al 2012). Parental care is highly variable (Clutton-Brock 1991;Royle et al 2012), reflecting that parents make flexible decisions about how much care to provide due to variation in the cost of care to themselves and/or the benefit to their offspring (Royle et al 2014;Ratz and Smiseth 2018). For example, parents are expected to provide less care should there be an increase in the cost of care, as shown by handicapping experiments on birds and insects (Wright and Cuthill 1989;Harrison et al 2009;Suzuki and Nagano 2009).…”

“…One potential explanation for why handicapped parents sometimes provide more care than control parents is that handicapping can trigger a shift towards greater investment in current reproduction (Ratz and Smiseth 2018), often referred to as terminal investment (Williams 1966;Clutton-Brock 1984). Theory suggests that terminal investment is triggered when an individual's condition deteriorates below a certain threshold value, thereby reducing its future survival prospects (Duffield et al 2017).…”