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1. Maternal death and offspring fitness in multiple wild primates

   https://doi.org/10.1073/pnas.2015317118  

   Zipple, Matthew N. ; Altmann, Jeanne ; Campos, Fernando A. ; Cords, Marina ; Fedigan, Linda M. ; Lawler, Richard R. ; Lonsdorf, Elizabeth V. ; Perry, Susan ; Pusey, Anne E. ; Stoinski, Tara S. ; et al ( December 2020 , Proceedings of the National Academy of Sciences)

   Primate offspring often depend on their mothers well beyond the age of weaning, and offspring that experience maternal death in early life can suffer substantial reductions in fitness across the life span. Here, we leverage data from eight wild primate populations (seven species) to examine two underappreciated pathways linking early maternal death and offspring fitness that are distinct from direct effects of orphaning on offspring survival. First, we show that, for five of the seven species, offspring face reduced survival during the years immediately preceding maternal death, while the mother is still alive. Second, we identify an intergenerational effect of early maternal loss in three species (muriquis, baboons, and blue monkeys), such that early maternal death experienced in one generation leads to reduced offspring survival in the next. Our results have important implications for the evolution of slow life histories in primates, as they suggest that maternal condition and survival are more important for offspring fitness than previously realized. 

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2. Higher early life mortality with lower infant body mass in a free‐ranging primate

   https://doi.org/10.1111/1365-2656.13291  

   Lee, D. Susie ; Mandalaywala, Tara M. ; Dubuc, Constance ; Widdig, Anja ; Higham, James P. ; Gaillard, ed., Jean‐Michel ( July 2020 , Journal of Animal Ecology)

   Traits that reflect the amount of energy allocated to offspring by mothers, such as infant body mass, are predicted to have long‐lasting effects on offspring fitness. In very long‐lived species, such as anthropoid primates, where long‐lasting and obligate parental care is required for successful recruitment of offspring, there are few studies on the fitness implications of low body mass among infants.

   Using body mass data collected from 253 free‐ranging rhesus macaqueMacaca mulattainfants on Cayo Santiago, Puerto Rico, we examined if lower infant body mass predicts lower chance of survival through to reproductive maturation (4th year of life). We also used data on inter‐birth intervals and suckling behaviours to determine whether the duration of maternal care was adjusted to infant body mass.

   Rhesus macaque infants experienced on average 5% reduced hazard of death for an increase in body mass of 0.1SD(~100 g) above the mean within their age–sex class. The positive association between body mass and early life survival was most pronounced in the 1st year of life.

   Infant body mass tended to be lower if mothers were young or old, but the link between infant body mass and early life survival remained after controlling for maternal age. This finding suggests that maternal effects on early life survival such as maternal age may act through their influence on infant body mass.

   Mothers of heavier infants were less likely to be delayed in subsequent reproduction, but the estimated association slightly overlapped with zero. The timing of the last week of suckling did not differ by infant body mass.

   Using infant body mass data that has been rarely available from free‐ranging primates, our study provides comparative evidence to strengthen the existing body of literature on the fitness implications of variation in infant body mass.

    

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3. Adult survival probability and body size affect parental risk‐taking across latitudes

   https://doi.org/10.1111/ele.13615  

   Oteyza, Juan_C ; Mouton, James_C ; Martin, Thomas_E ; Sorci, ed., Gabriele ( October 2020 , Ecology Letters)

   Parents faced with a predator must choose between their own safety versus taking care of their offspring. Each choice can have fitness costs. Life‐history theory predicts that longer‐lived species should be less willing than shorter‐lived species to return to care for their offspring after a predator disturbance because they have more opportunities to reproduce in the future. We increased adult predation risk during incubation for 40 bird species in north temperate, tropical, and south temperate latitudes. We found that species with higher adult survival probabilities were more cautious, waiting longer before returning to the nest to provide care. Contrary to other studies, we also found that parents were more risk averse and waited longer to return in smaller than larger species, likely reflecting greater vulnerability of smaller species. Ultimately, the relative risk a predator poses to a species and the probability of future reproduction predict parental risk taking across the world.

    

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4. An acute dose of intranasal oxytocin rapidly increases maternal communication and maintains maternal care in primiparous postpartum California mice

   https://doi.org/10.1371/journal.pone.0244033  

   Guoynes, Caleigh D. ; Marler, Catherine A. ( April 2021 , PLOS ONE)

   Rosenfeld, Cheryl S. (Ed.)

   Maternal-offspring communication and care are essential for offspring survival. Oxytocin (OXT) is known for its role in initiation of maternal care, but whether OXT can rapidly influence maternal behavior or ultrasonic vocalizations (USVs; above 50 kHz) has not been examined. To test for rapid effects of OXT, California mouse mothers were administered an acute intranasal (IN) dose of OXT (0.8 IU/kg) or saline followed by a separation test with three phases: habituation with pups in a new testing chamber, separation via a wire mesh, and finally reunion with pups. We measured maternal care, maternal USVs, and pup USVs. In mothers, we primarily observed simple sweep USVs, a short downward sweeping call around 50 kHz, and in pups we only observed pup whines, a long call with multiple harmonics ranging from 20 kHz to 50 kHz. We found that IN OXT rapidly and selectively enhanced the normal increase in maternal simple sweep USVs when mothers had physical access to pups (habituation and reunion), but not when mothers were physically separated from pups. Frequency of mothers’ and pups’ USVs were correlated upon reunion, but IN OXT did not influence this correlation. Finally, mothers given IN OXT showed more efficient pup retrieval/carrying and greater total maternal care upon reunion. Behavioral changes were specific to maternal behaviors (e.g. retrievals) as mothers given IN OXT did not differ from controls in stress-related behaviors (e.g. freezing). Overall, these findings highlight the rapid effects and context-dependent effect a single treatment with IN OXT has on both maternal USV production and offspring care. 

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5. Development and the effects of extended parenting in the cold‐breeding burying beetle Nicrophorus sayi

   https://doi.org/10.1111/een.12670  

   Benowitz, Kyle M. ; Amukamara, Ashley U. ; Mckinney, Elizabeth C. ; Moore, Allen J. ( August 2018 , Ecological Entomology)

   1. Burying beetles (Nicrophorusspp.) provide an excellent model system to test predictions about the relationships between environment, life‐history and behaviour. All species in the genus display similar natural histories, breeding on vertebrate carcasses and providing parental care to developing offspring. However, variations in other aspects of species' ecologies provide a rich framework to examine the evolution of parental behaviours and other traits.

   2. One little‐studied species,N. sayi, breeds in substantially colder temperatures than its congeners, creating a potentially harsh environment for offspring. Here, we examined the timing of reproductive and developmental events in this species, and also investigated the effects of removing parents on offspring performance.

   3. We find that development is not only extremely slow in this species, but it is also delayed even in comparison to other burying beetles reared at similar temperatures. However, the presence of parents reduces the time that offspring take to leave the carcass. This decrease in development time does not appear to result in a trade‐off with mortality or body size.

   4. From these results, we suggest that very slow development may be advantageous when living in a particularly cold environment. Additionally, one role of extended parental care may be to assist offspring in dealing with these harsh conditions, and to mitigate the potentially negative consequences of adopting such a slow life‐history strategy.

    

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