scholarly journals Maternal glucocorticoids have minimal effects on HPA axis activity and behavior of juvenile wild North American red squirrels

2021 ◽  
Author(s):  
Sarah E. Westrick ◽  
Freya van Kesteren ◽  
Stan Boutin ◽  
Jeffrey E. Lane ◽  
Andrew G. McAdam ◽  
...  
Keyword(s):  
Hpa Axis ◽  
Negative Feedback ◽  
North American ◽  
Developmental Plasticity ◽  
Early Lactation ◽  
Red Squirrels ◽  
Treatment Groups ◽  
North American Red Squirrels ◽  
And Behavior ◽  
The Impact

As a response to environmental cues, maternal glucocorticoids (GCs) may trigger adaptive developmental plasticity in the physiology and behavior of offspring. In North American red squirrels (Tamiasciurus hudsonicus), mothers exhibit increased GCs when conspecific density is elevated, and selection favors more aggressive and perhaps more active mothers under these conditions. We tested the hypothesis that elevated maternal GCs cause shifts in offspring behavior that may prepare them for high density conditions. We experimentally elevated maternal GCs during gestation or early lactation. We measured two behavioral traits (activity and aggression) in weaned offspring using standardized behavioral assays. Because maternal GCs may influence offspring hypothalamic-pituitary-adrenal (HPA) axis dynamics, which may in turn affect behavior, we also measured the impact of our treatments on offspring HPA axis dynamics (adrenal reactivity and negative feedback), and the association between offspring HPA axis dynamics and behavior. Increased maternal GCs during lactation, but not gestation, slightly elevated activity levels in offspring. Offspring aggression and adrenal reactivity did not differ between treatment groups. Male, but not female, offspring from mothers treated with GCs during pregnancy exhibited stronger negative feedback compared to those from control mothers, but there were no differences in negative feedback between lactation treatment groups. Offspring with higher adrenal reactivity from mothers treated during pregnancy (both controls and GC-treated) exhibited lower aggression and activity. These results suggest maternal GCs during gestation or early lactation alone may not be a sufficient cue to produce substantial changes in behavioral and physiological stress responses in offspring in natural populations.

scholarly journals Maternal glucocorticoids do not influence HPA axis activity or behavior of juvenile wild North American red squirrels

2020 ◽  
Author(s):  
Sarah E Westrick ◽  
Freya van Kesteren ◽  
Stan Boutin ◽  
Jeffrey E Lane ◽  
Andrew G McAdam ◽  
...  
Keyword(s):  
Hpa Axis ◽  
Negative Feedback ◽  
North American ◽  
High Density ◽  
Early Lactation ◽  
Red Squirrels ◽  
North American Red Squirrels ◽  
And Behavior ◽  
Hpa Axis Activity ◽  
The Impact

AbstractEnvironmental factors experienced during development can affect the physiology and behavior of offspring. Maternal glucocorticoids (GCs) may convert environmental cues experienced by the mother into a cue triggering adaptive developmental plasticity in offspring. In North American red squirrels (Tamiasciurus hudsonicus), females exhibit increases in GCs when conspecific density is elevated, and selection favors more aggressive and perhaps more active mothers under high density conditions. We experimentally elevated maternal GCs during gestation or early lactation to test the hypothesis that elevated maternal GCs cause shifts in offspring aggression and activity that may prepare them for high density conditions. When offspring were weaned, we measured two behavioral traits (activity and aggression) using a standardized behavioral assay. Because maternal GCs may influence offspring hypothalamic-pituitary-adrenal (HPA) axis activity and HPA axis activity may in turn affect offspring behavior, we also measured the impact of our treatments on offspring HPA axis activity (adrenal reactivity and negative feedback) and the association between offspring HPA axis activity and behavior. Increased maternal GCs during lactation, but not gestation, only slightly elevated activity levels in offspring. Offspring aggression, adrenal reactivity, and negative feedback did not differ between GC-treated and control groups. Offspring with higher adrenal reactivity did exhibit lower aggression, but the relationship between adrenal reactivity and aggression was not affected by treatment with maternal GCs. These results suggest maternal GCs during gestation or early lactation alone may not be a sufficient cue to produce changes in behavioral and physiological stress responses in offspring in natural populations.Summary StatementWe found maternal glucocorticoid levels do not influence offspring personality or HPA axis dynamics in North American red squirrels. Regardless of maternal glucocorticoid treatment, more aggressive squirrels exhibited lower adrenal reactivity.

scholarly journals Why do North American Red Squirrel, Tamiasciurus hudsonicus, Mothers Relocate Their Young? A Predation-based Hypothesis

2008 ◽  
Vol 122 (1) ◽  
pp. 65 ◽  
Author(s):  
Tricia Kerr ◽  
Sébastien Descamps
Keyword(s):  
North American ◽  
Tamiasciurus Hudsonicus ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Efficient Strategy ◽  
North American Red Squirrels ◽  
The Impact ◽  
North American Red Squirrel

Our study reports the first observations consistent with Short-Tailed Weasel predation on juvenile North American Red Squirrels in the nest. Red Squirrel mothers are known to relocate their young to another nest after a disturbance. We suggest that this behaviour might be an efficient strategy that reduces the impact of litter depredation by weasels.

Constraints on First Reproduction in North American Red Squirrels

Oikos ◽  
1998 ◽  
Vol 81 (1) ◽  
pp. 81 ◽  
Author(s):  
C. Dustin Becker ◽  
Stan Boutin ◽  
Karl W. Larsen
Keyword(s):  
North American ◽  
Red Squirrels ◽  
First Reproduction ◽  
North American Red Squirrels

North American red squirrels mitigate costs of territory defence through social plasticity

2019 ◽  
Vol 151 ◽  
pp. 29-42 ◽  
Author(s):  
Erin R. Siracusa ◽  
David R. Wilson ◽  
Emily K. Studd ◽  
Stan Boutin ◽  
Murray M. Humphries ◽  
...  
Keyword(s):  
North American ◽  
Red Squirrels ◽  
Territory Defence ◽  
Social Plasticity ◽  
North American Red Squirrels

scholarly journals The effects of stress and glucocorticoids on vocalizations: a test in North American red squirrels

2019 ◽  
Vol 30 (4) ◽  
pp. 1030-1040 ◽  
Author(s):  
Matt Sehrsweeney ◽  
David R Wilson ◽  
Maggie Bain ◽  
Stan Boutin ◽  
Jeffrey E Lane ◽  
...  
Keyword(s):  
Stress State ◽  
North American ◽  
Physiological Stress ◽  
Physiological State ◽  
Public Information ◽  
Tamiasciurus Hudsonicus ◽  
Red Squirrels ◽  
Acoustic Structure ◽  
North American Red Squirrels ◽  
Important Means

AbstractAcoustic signaling is an important means by which animals communicate both stable and labile characteristics. Although it is widely appreciated that vocalizations can convey information on labile state, such as fear and aggression, fewer studies have experimentally examined the acoustic expression of stress state. The transmission of such public information about physiological state could have broad implications, potentially influencing the behavior and life-history traits of neighbors. North American red squirrels (Tamiasciurus hudsonicus) produce vocalizations known as rattles that advertise territorial ownership. We examined the influence of changes in physiological stress state on rattle acoustic structure through the application of a stressor (trapping and handling the squirrels) and by provisioning squirrels with exogenous glucocorticoids (GCs). We characterized the acoustic structure of rattles emitted by these squirrels by measuring rattle duration, mean frequency, and entropy. We found evidence that rattles do indeed exhibit a “stress signature.” When squirrels were trapped and handled, they produced rattles that were longer in duration with a higher frequency and increased entropy. However, squirrels that were administered exogenous GCs had similar rattle duration, frequency, and entropy as squirrels that were fed control treatments and unfed squirrels. Our results indicate that short-term stress does affect the acoustic structure of vocalizations, but elevated circulating GC levels do not mediate such changes.

scholarly journals Indirect effects on fitness between individuals that have never met via an extended phenotype

2018 ◽  
Author(s):  
David N. Fisher ◽  
Jessica A. Haines ◽  
Stan Boutin ◽  
Ben Dantzer ◽  
Jeffrey E. Lane ◽  
...  
Keyword(s):  
Population Dynamics ◽  
North American ◽  
Indirect Effects ◽  
Tamiasciurus Hudsonicus ◽  
Extended Phenotype ◽  
Red Squirrels ◽  
Lifetime Fitness ◽  
The Past ◽  
North American Red Squirrels ◽  
The Individual

AbstractInteractions between organisms are ubiquitous and have important consequences for phenotypes and fitness. Individuals can even influence those they never meet, if they have extended phenotypes which mean the environments others experience are altered. North American red squirrels (Tamiasciurus hudsonicus) guard food hoards, an extended phenotype that typically outlives the individual and is almost always inherited by non relatives. Hoarding by previous owners can therefore influence subsequent owners. We found that red squirrels bred earlier and had higher lifetime fitness if the previous owner was a male. This was driven by hoarding behaviour, as males and mid-aged squirrels had the largest hoards, and these effects persisted across owners, such that if the previous owner was male or died in mid-age subsequent occupants had larger hoards. Individuals can, therefore, influence each other’s resource dependent traits and fitness without meeting via extended phenotypes, and so the past can influence contemporary population dynamics.

scholarly journals Glucocorticoids coordinate changes in gut microbiome composition in wild North American red squirrels

2021 ◽  
Author(s):  
Lauren Petrullo ◽  
Tiantian Ren ◽  
Martin Wu ◽  
Rudy Boonstra ◽  
Rupert Palme ◽  
...  
Keyword(s):  
Microbial Diversity ◽  
North American ◽  
Gut Microbiome ◽  
Pathogenic Bacteria ◽  
Experimental Studies ◽  
Ecological Framework ◽  
Ecological Change ◽  
Red Squirrels ◽  
Microbiome Diversity ◽  
North American Red Squirrels

Gut microbiome diversity plays an important role in host health and fitness, in part through the diversification of gut metabolic function and pathogen protection. Elevations in glucocorticoids (GCs) appear to reduce gut microbiome diversity in experimental studies, suggesting that a loss of microbial diversity may be a negative consequence of increased GCs. However, given that ecological factors like food availability and population density may independently influence both GCs and microbial diversity, understanding how these factors structure the GC-microbiome relationship is crucial to interpreting its significance in wild populations. Here, we used an ecological framework to investigate the relationship between GCs and gut microbiome diversity in wild North American red squirrels (Tamiasciurus hudsonicus). We found that higher GCs predicted lower gut microbiome diversity and an increase in metabolic taxa. In addition, we identified a loss of potentially pathogenic bacteria with increasing GCs. Both dietary heterogeneity and an upcoming masting event exhibited direct effects on gut microbiome diversity, whereas conspecific density and host reproductive activity impacted diversity indirectly via changes in GCs. Together, our results suggest that GCs coordinate the effects of ecological change and host biology on gut microbiome diversity, and highlight the importance of situating the GC-microbiome relationship within an ecological framework.

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