Biology subjects

Laubach, Z. M.

Publications and source records attributed to Laubach, Z. M..

6 recordsLinked to original sources

bioRxiv2025

The effects of temperature on nestling growth in a songbird depend on developmental and social context

Climate change can adversely impact animals, especially those that cannot independently thermoregulate or avoid exposure. Cold, hot, and variable temperatures may impede nestling songbird growth due to increased thermoregulatory costs and reduced food delivery by parents. At a broad scale, temperature effects on nestling growth vary across climatic zones, but how temperature effects vary with early-life developmental constraints imposed by the timing of thermoregulatory development, competition with siblings, and the amount of parental care has received less attention. We investigated whether the effect of temperature on the mass of wild barn swallow (Hirundo rustica erythrogaster) nestlings (n = 113 nestlings, 31 nests) in Boulder County, CO depends on timing of exposure during development, relative size within the brood, or level of parental feeding. We found that the effect of minimum temperature differed in early and late development (before versus after putative development of thermoregulatory independence) and may be less pronounced for nestlings that received more parental feeding. We did not find evidence that the smallest nestling in the brood differs from other nestlings in vulnerability to temperature. These findings indicate the existence of fine-scale heterogeneity in which the effects of temperature on nestling development are sensitive to metabolic constraints and early-life social environment, providing key insight into the factors that may ameliorate or exacerbate climate impacts on individual birds.

ecology↗

bioRxiv2025

Testing the mediating role of female-male social interactions on the relationship between age and reproductive success.

Differential reproduction is a key driver of evolution that is determined by individual characteristics and mating opportunities, including mate choice. Social interactions between conspecifics are hypothesized to be important in facilitating mate choice and reproductive success but are difficult to measure. Using data from 52 adult barn swallows (Hirundo rustica erythrogaster), whose social interactions were measured via proximity tags, we tested the hypothesis that social interactions mediate the relationship between age (a proxy for experience) and condition-dependent plumage traits, and their associations with reproductive success. We found that older female barn swallows had higher fecundity and that older males have higher paternity. Older males achieved higher paternity through extra pair copulations, not by greater paternity with their social mate. Longer tail streamers were associated with greater fecundity/paternity in both sexes, but this effect was independent of age only among females. Darker ventral plumage coloration was not associated with higher reproductive success in either sex. We also observed that older birds appear to be less social with conspecifics, as indicated by fewer numbers of social interactions, though these associations were only marginally significant in males. Interestingly, females with fewer social interactions had higher fecundity. Finally, we found no evidence of mediation by the number of social interactions. Taken together, our results suggest that older, more experienced birds can produce more offspring while being less social.

animal behavior and cognition↗

bioRxiv2024

Parental care modifies the role of early-life size and growth in shaping future physiology

Size and growth early in life are associated with physiological development and these traits influence fitness. Life history theory predicts that the relationship between traits reflect constraints involving allocation and acquisition of resources. Using longitudinal data from 113 wild nestling barn swallows (Hirundo rustica erythrogaster), we first characterized developmental changes in glucose metabolism, a physiological trait involved in energy mobilization and response to stress. Next, we used these data to test hypotheses from life history theory about allocation and acquisition of resources based on associations of nestling size and growth with glucose physiology and assessed whether these relationships are modified by parental care. We found that larger nestlings had higher baseline blood glucose and larger magnitude of change in glucose in response to a stressor. Further, this relationship was most pronounced among birds in nests that received the lowest amount of parental care. Given that glucose metabolism fuels activity and is critical in the vertebrate stress response, these results suggest that physiological constraints may contribute to the early-life disadvantage of being smaller, especially in the context of lower parental care. While these findings are inconsistent with a trade-off involving differential allocation of resources between life history traits, they align with the differential acquisition hypothesis.

evolutionary biology↗

bioRxiv2021

Measuring salivary cortisol in wild carnivores

Salivary hormone analyses provide a useful alternative to fecal and urinary hormone analyses in non-invasive studies of behavioral endocrinology. Here, we use saliva to assess cortisol levels in a wild population of spotted hyenas (Crocuta crocuta), a gregarious carnivore living in complex social groups. We first describe a novel, non-invasive method of collecting saliva from juvenile hyenas and validate a salivary cortisol assay for use in this species. We then analyze over 260 saliva samples collected from nearly 70 juveniles to investigate the relationships between cortisol and temporal and social variables in these animals. We obtain evidence of a bimodal daily rhythm with salivary cortisol concentrations dropping around dawn and dusk, times at which cub activity levels are changing substantially. We also find that dominant littermates have lower cortisol than either subordinate littermates or singletons, but that cortisol does not vary with age, sex, or maternal social rank. Finally, we examine how social behaviors such as aggression or play affect salivary cortisol concentrations. We find that inflicting aggression on others was associated with lower cortisol concentrations. We hope that the detailed description of our methods provides wildlife researchers with the tools to measure salivary cortisol in other wild carnivores. HIGHLIGHTSO_LIWe validated methods for collecting and analyzing saliva from wild carnivores. C_LIO_LIWe documented a bimodal daily rhythm in juvenile spotted hyena salivary cortisol. C_LIO_LICortisol varied among juvenile hyenas based on litter size and intra-litter rank. C_LIO_LIInflicting aggression on others was associated with lower cortisol concentrations. C_LI

zoology↗

bioRxiv2020

Toxoplasma gondii infections are associated with boldness towards lions in wild hyena hosts

Toxoplasma gondii is widely reported to manipulate the behavior of its non-definitive hosts in ways that promote lethal interactions with the parasites definitive feline hosts. Nonetheless, there is a lack of data on the association between T. gondii infection and costly behavioral interactions with felids in nature. Here, we report that three decades of field observations reveal T. gondii infected hyena cubs approach lions more closely than uninfected peers and have higher rates of lion mortality. Our findings support the hypothesis that T. gondiis manipulation of host boldness is an extended phenotype that promotes parasite transmission from intermediate hosts to feline predators. While upregulating hyena boldness toward lions might achieve this, it may also reflect a collateral influence of manipulative traits that evolved in other hosts (e.g., rodents). In either case, our findings corroborate the potential impacts of a globally distributed and generalist parasite (T. gondii) on fitness-related interaction with felids in a wild host. One Sentence SummaryWild hyenas infected with the parasite T. gondii show evidence of costly behavioral manipulation when interacting with lions.

animal behavior and cognition↗

bioRxiv2020

Associations of early social experience with offspring DNA methylation and later life stress phenotype

In a wild population of spotted hyenas, we tested the hypothesis that maternal care during the first year of life and social connectedness during two periods of early development lead to differences in DNA methylation and fecal glucocorticoid metabolites (fGCMs) later in life. We found that although maternal care and social connectedness during the communal den dependent period were not associated with fGCMs, greater social connectedness after hyenas leave their communal den is associated with lower adult fGCMs. Additionally, more maternal care and social connectedness after leaving the communal den corresponded with higher global (%CCGG) DNA methylation. Finally, we identified multiple DNA methylation biomarkers near genes involved in inflammation that may link maternal care and stress phenotype. Our findings suggest that both maternal care during the first year of life and social connections after leaving the den influence DNA methylation and contribute to a developmentally plastic stress response.

animal behavior and cognition↗