Parental care is a key component of an organism’s reproductive strategy that is thought to trade-off with allocation towards immunity. Yet it is unclear how caring parents respond to pathogens: do infected parents reduce care as a sickness behaviour or simply from being ill, or do they prioritise their offspring by maintaining high levels of care? To address this issue, we investigated the consequences of infection by the pathogen Serratia marcescens on mortality, time spent providing care, reproductive output, and expression of immune genes of female parents in the burying beetle Nicrophorus vespilloides. We compared untreated control females with infected females that were inoculated with live bacteria, immune-challenged females that were inoculated with heat-killed bacteria, and injured females that were injected with buffer. We found that infected and immune-challenged females changed their immune gene expression and that infected females suffered increased mortality. Nevertheless, infected and immune-challenged females maintained their normal level of care and reproductive output. There was thus no evidence that infection led to either a decrease or an increase in parental care or reproductive output. Our results show that parental care, which is generally highly flexible, can remain remarkably robust and consistent despite the elevated mortality caused by infection by pathogens. Overall, these findings suggest that infected females maintain a high level of parental care; a strategy that may ensure that offspring receive the necessary amount of care but that might be detrimental to the parents’ own survival or that may even facilitate disease transmission to offspring.

The spreadsheets provide data of two separate experiments conducted in the burying beetle Nicrophorus vespilloides. The first one includes data on the effects of an experimental treatments applied to female parents (control = Handled, injury = PBS, immune-challenged = Heat.killed, infected = S.marc) on their parental behavior, on weight change and on the performance of their larvae. It also includes informaiton on the brood and female identity (brood_id, female_id). Weights and masses were measured in grams, brood sizes in number of individual larvae, female life span in number of days between eclosion and death for adult life span (adult_lifespan) and in number of days between infection and death for post-infection life span (postinfection_lifespan). Female behaviour measured on the day after larval hatching (maintenance, feeding) represent a number of scans between 0 and 30. Total care was then calculated as the sum of maintenance and feeding. Note that the analysis was conducted on data excluding the broods for which the female was used to sample hemolymph (hemolym_extracted) for quantifying immune gene expression presented in Data_immune_gene_expression_data.csv. We also excluded data rows (to_exclude) from some analyses data rows because eggs failed to hatch, females could not be allocated a brood, the female or the whole brood died, no behavioural data were collected, the treatment failed, or hemolymph samples were too small (see Methods in the article for details). Missing data are recorded as NAs.

The second dataset incudes data on the effects of the same experimental treatments on the relative expression of immune genes, abbreviated as: D_CT_Att = Δ_CTattacin-4, C_CT_CEC = Δ_CTcecropin-1, C_CT_Col = Δ_CTcoleoptericin-1, C_CT_PGRP = Δ_CTPGRP-SC2. Missing data are recorded as NAs.