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1. Experimental increases in temperature mean and variance alter reproductive behaviours in the dung beetle Phanaeus vindex

   https://doi.org/10.1098/rsbl.2022.0109  

   Kirkpatrick, William H.; Sheldon, Kimberly S. (July 2022, Biology Letters)

   Temperature profoundly impacts insect development, but plasticity of reproductive behaviours may mediate the impacts of temperature change on earlier life stages. Few studies have examined the potential for adult behavioural plasticity to buffer offspring from the warmer, more variable temperatures associated with climate change. We used a field manipulation to examine whether the dung beetle Phanaeus vindex alters breeding behaviours in response to temperature changes and whether behavioural shifts protect offspring from temperature changes. Dung beetles lay eggs inside brood balls made of dung that are buried underground. Brood ball depth impacts the temperatures offspring experience with consequences for development. We placed adult females in either control or greenhouse treatments that simultaneously increased temperature mean and variance. We found that females in greenhouse treatments produced more brood balls that were smaller and buried deeper than controls, suggesting brood ball number or burial depth may come at a cost to brood ball size, which can impact offspring nutrition. Despite being buried deeper, brood balls from the greenhouse treatment experienced warmer mean temperatures but similar amplitudes of temperature fluctuation relative to controls. Our findings suggest adult behaviours may partially buffer developing offspring from temperature changes. 

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2. Behavioral plasticity of dung beetle species in warmer, more variable temperatures impacts fitness

   Sheldon, Kimberly S (March 2023, Integrative & Comparative Biology)

   Temperature strongly affects insect development, but plasticity of adult reproductive behaviors can alter the temperatures experienced by earlier life stages. To date, few studies have tested whether adult behavioral plasticity can protect offspring from the warmer,more variable temperatures linked to climate change. Here I discuss laboratory experiments and field manipulations in which my lab has examined whether the adults of three dung beetle species modify their breeding behaviors in response to increases in temperature mean and variance and whether these behavioral shifts can protect dung beetle offspring from temperature changes. Tunnelling dung beetles lay their eggs inside brood balls constructed of dung that are buried below the soil surface. The depth of the brood ball affects the temperatures that the offspring experience and, thus, offspring development. Based on lab and field studies, all three species placed brood balls deeper in the soil in response to warmer and more variable temperatures, but for some species, the greater burial depth came at a cost to brood ball size and/or number, which can impact fitness. Despite greater burial depths, offspring in brood balls in the heated treatments still experienced warmer mean temperatures, which had a large, negative effect on offspring survival of the species with the smallest body size. These findings suggest adult behaviors could partially shield developing offspring from temperature changes. 

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3. The impacts of climate change on secondary seed dispersal in dung beetles

   Duerr, Nathan; Sheldon, Kimberly S (May 2024, Integrative and Comparative Biology)

   Dung beetles, which move and bury the feces of vertebrates, are major drivers of ecosystem processes and provide crucial ecosystem services, including secondary seed dispersal. Dung beetles bury seed-containing dung in food caches or in brood balls used for breeding purposes, but little is known about how this behavior will be affected by climate change. We utilized field manipulations to investigate the effect of simulated climate change—including simultaneous increases in temperature mean and variance—on the seed dispersal behavior of two tunneling dung beetle species, Phanaeus vindex and Onthophagus taurus. We placed single adult females into either control or greenhouse treatments along with temperature loggers. We mixed glass beads of three sizes into cow dung to mimic seeds, provided beetles with the dung, and then allowed them to bury dung for either six or nine days. At the end of each trial, we recorded information on dung deposits, including the type (i.e., food cache or brood ball), number, size, burial depth, and the amount of each bead size found in the deposit. We found differences in burial depths of brood balls and food caches within species, as well as differences in the size and amount of beads buried between species. Exposure to higher temperatures resulted in brood balls being buried deeper across species, but did not change the burial depth of food caches. 

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4. Behavioural responses to warming differentially impact survival in introduced and native dung beetles

   https://doi.org/10.1111/1365-2656.13366  

   Mamantov, Margaret_A; Sheldon, Kimberly_S; Behmer, ed., Spencer (October 2020, Journal of Animal Ecology)

   Abstract Anthropogenic changes are often studied in isolation but may interact to affect biodiversity. For example, climate change could exacerbate the impacts of biological invasions if climate change differentially affects invasive and native species. Behavioural plasticity may mitigate some of the impacts of climate change, but species vary in their degree of behavioural plasticity. In particular, invasive species may have greater behavioural plasticity than native species since plasticity helps invasive species establish and spread in new environments. This plasticity could make invasives better able to cope with climate change.Here our goal was to examine whether reproductive behaviours and behavioural plasticity vary between an introduced and a nativeOnthophagusdung beetle species in response to warming temperatures and how differences in behaviour influence offspring survival.Using a repeated measures design, we exposed small colonies of introducedO. taurusand nativeO. hecateto three temperature treatments, including a control, low warming and high warming treatment, and then measured reproductive behaviours, including the number, size and burial depth of brood balls. We reared offspring in their brood balls in developmental temperatures that matched those of the brood ball burial depth to quantify survival.We found that the introducedO. taurusproduced more brood balls and larger brood balls, and buried brood balls deeper than the nativeO. hecatein all treatments. However, the two species did not vary in the degree of behavioural plasticity in response to warming. Differences in reproductive behaviours did affect survival such that warming temperatures had a greater effect on survival of offspring of nativeO. hecatecompared to introducedO. taurus.Overall, our results suggest that differences in behaviour between native and introduced species are one mechanism through which climate change may exacerbate negative impacts of biological invasions. 

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5. Visitation rate, but not foraging range, responds to brood size manipulation in an aerial insectivore

   https://doi.org/10.1007/s00265-022-03244-z  

   Madden, Sage A.; McDermott, Molly T.; Safran, Rebecca J. (September 2022, Behavioral Ecology and Sociobiology)

   AbstractLife history theory predicts that increased investment in current offspring decreases future fecundity or survival. Avian parental investment decisions have been studied either via brood size manipulation or direct manipulation of parental energetic costs (also known as handicapping). However, we have limited experimental data on the potential interactive effects of these manipulations on parent behavior. Additionally, we know little about how these manipulations affect spatial foraging behavior away from the nest. We simultaneously manipulated brood size and parental costs (via added weight in the form of a GPS tag) in wild female barn swallows (Hirundo rustica). We measured multiple aspects of parent behavior at and away from the nest while controlling for measures of weather conditions. We found no significant interactive effects of manipulated brood size and parental costs. Both sexes increased their visitation rate with brood size, but nestlings in enlarged broods grew significantly less post-brood size manipulation than those in reduced broods. Foraging range area was highly variable among GPS-tagged females but was unaffected by brood size. As such, increased visitation rate in response to brood size may be more energetically costly for far-ranging females. GPS-tagged females did not alter their visitation rate relative to un-tagged birds, but their mates had higher visitation rates. This suggests that GPS tagging may affect some unmeasured aspect of female behavior, such as prey delivery. Our findings indicate that investigation of foraging tactics alongside visitation rate is critical to understanding parental investment and the benefits and costs of reproduction. Significance statementAvian parental investment decisions have been studied by either brood size manipulation or direct manipulation of parental costs, but rarely both simultaneously. We simultaneously manipulated brood size and parental costs (via addition of a GPS tag) in a wild avian system, allowing us to examine interactive effects of these manipulations. Additionally, studies of parental investment often examine behaviors at the nest, but measurements of parental care behavior away from the nest are rare. Our study is unique in that we measured multiple aspects of parental care, including spatial foraging behavior tracked with GPS tags. We found no interactive effects of manipulated brood size and parental costs on visitation rate or nestling growth, and spatial foraging behavior of females was individually variable. Documenting foraging tactics alongside visitation rate is critical to understanding parental investment because the same visitation rate might be more costly for far-ranging females. 

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