Managing anabolic steroids in pre-hibernating Arctic ground squirrels: obtaining their benefits and avoiding their costs

Boonstra, Rudy; Mo, Kaiguo; Monks, D. Ashley

doi:10.1098/rsbl.2014.0734

Cited by 11 publications

(3 citation statements)

References 15 publications

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“…Environmental pressures can alter the interaction between testosterone and body weight. For example, arctic ground squirrels survive hibernation in the tundra with higher endogenous levels of androgen receptor relative to other ground squirrels, allowing them to increase their muscle mass prior to winter (Boonstra et al, 2014). When accounting for the effect of body weight, there is no relationship between phenotype and testosterone level (Table 2).…”

Section: Discussionmentioning

confidence: 99%

Hormones do not make the mole-rat: no steroid hormone signatures of subordinate behavioral phenotypes

Faykoo-Martinez

Toor

Edwards

et al. 2022

Preprint

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In some cooperatively breeding groups, individuals have distinct behavioral characteristics that are often stable and predictable across time. However, in others, like the eusocial naked mole-rat, evidence for behavioral phenotypes is ambiguous. Here, we study whether the naked mole-rat can be divided into discrete phenotypes and if circulating hormone levels underpin these differences. Naked mole-rat colonies consist of a single breeding female and dozens to hundreds of non-reproductive subordinates. The subordinates can potentially be divided into soldiers, who defend the colony; workers, who maintain it; and dispersers, who want to leave it. We established six colonies de novo, tracked them over three years, and assessed the behavior and hormone levels of the subordinates. We found that soldiers tended to be from earlier litters and were higher ranked compared to workers, whereas dispersers were distributed throughout litters and rankings. There was no difference in estradiol, testosterone, or dehydroepiandrosterone (DHEA) levels amongst phenotypes. Progesterone levels were higher in soldiers but this difference appeared to be driven by a few individuals. Principal component analysis demonstrated that soldiers separated into a discrete category relative to workers/dispersers, with the highest ranked loadings being age, weight, and testosterone levels. However, the higher testosterone in soldiers was correlated with large body size instead of strictly behavioral phenotype. Workers and dispersers have more overlap with each other and no hormonal differences. Thus the behavioral variation in subordinate naked mole-rats is likely not driven by circulating steroid hormone levels but rather stems from alternative neural and/or neuroendocrine mechanisms.

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Section: Discussionmentioning

confidence: 99%

Hormones do not make the mole-rat: no steroid hormone signatures of subordinate behavioral phenotypes

Faykoo-Martinez

Toor

Edwards

et al. 2022

Preprint

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“…Boonstra et al (2011; 2014) have proposed an anabolic function and need for circulating androgens in AGS in late summer. They propose that elevated androgens and the localization of androgen receptors enable AGS to increase their lean mass in preparation for hibernation.…”

Section: Discussionmentioning

confidence: 99%

The influence of androgens on hibernation phenology of free-living male arctic ground squirrels

Richter

Barnes

O’Reilly

et al. 2017

Hormones and Behavior

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Free-living ground squirrel species are sexually dimorphic in hibernation phenology. The underlying causes of these differences are not yet known. Androgens, testosterone (T) in particular, inhibit hibernation. To determine the influence of endogenous androgens on annual timing of hibernation we first measured circulating levels of T and dehydroepiandrosterone (DHEA), an adrenal androgen implicated in non-mating season aggression in other species, in free-living male arctic ground squirrels (Urocitellus parryii, AGS). We also manipulated endogenous androgen levels by surgical castration, and consequently compared body temperature records from intact (n = 24) and castrated (n = 9) males to elucidate the influence of endogenous androgens on annual body temperature cycles. The highest T levels (0.53 ± 0.10 ng/mL) were in reproductively mature male AGS in spring; whereas, both immature males in spring and all males in late summer had T levels an order of magnitude lower (0.07 ± 0.01 and 0.06 ± 0.00 ng/mL, respectively). DHEA levels were higher in males during the late summer compared to reproductively mature males in spring (120.6 ± 18.9 and 35.9 ± 2.3 pg/mL, respectively). Eliminating gonadal androgens via castration resulted in males delaying euthermy by extending heterothermy significantly in spring (Apr 22 ± 2.9) than reproductive males (Mar 28 ± 3.9) but did not change the timing of hibernation onset (castrate: Oct 12 ± 1.0 vs. intact: Oct 3 ± 3.1). We conclude that while androgens play a significant role in spring hibernation phenology of males, their role in fall hibernation onset is unclear.

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“…We hypothesize that being in poor spring body condition may influence reproduction and active-season survival. AGS under heightened pressure to achieve sufficient fat and muscle reserves (Boonstra et al 2014) to survive a long hibernation period likely forego strategies that maximize short-term survival (vigilance) for behaviours intended to ensure successful hibernation (foraging). The prioritization of foraging over safety could be expressed in two ways.…”

Section: Mass Gainmentioning

confidence: 99%

Forest or meadow: the consequences of habitat for the condition of female arctic ground squirrels (Urocitellus parryii plesius)

2015

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Body condition of animals influences the likelihood of surviving harsh environmental conditions, successfully reproducing, and resisting disease. The sum of these individual components of fitness, in turn, have consequences for the growth and persistence of wildlife populations. Here we compared the body mass and condition of adult female arctic ground squirrels (Urocitellus parryii plesius (Osgood, 1900)), an obligate hibernator, in source and sink habitats. We tested the hypothesis that adult females would be in poorer condition in the boreal forest than in adjacent meadows. We found that, during spring, postpartum females in forests weighed less (405 ± 7 vs. 437 ± 11 g; mean ± SE) and were in poorer condition (mean (±SE) residual of mass over structural size = −11.0 ± 10.2 vs. 20.5 ± 6.1 g) compared with females in meadow-source habitat. However, by the onset of entrance into hibernation in August, forest squirrels had reached parity with meadow squirrels and no difference was found in mass (519 ± 13 vs. 520 ± 15 g; mean ± SE) or condition (residual index = −0.01 ± 0.01 vs. 0.03 ± 0.01; mean ± SE). We suggest that for squirrels in formerly occupied boreal forests, (i) poor spring body condition decreased reproductive success and (ii) achieving compensatory growth, via increased foraging, comes at the costs of higher predation risk. These costs likely contributed to the recent local extinction of arctic ground squirrels in boreal forest habitat.Résumé : L'embonpoint des animaux influence la probabilité de survie dans des conditions ambiantes difficiles, le succès de reproduction et la résistance aux maladies. La somme de ces différentes composantes de l'aptitude a, quant à elle, des conséquences en ce qui concerne la croissance et la persistance des populations d'animaux sauvages. Nous comparons la masse corporelle et l'embonpoint de spermophiles arctiques (Urocitellus parryii plesius (Osgood, 1900)) femelles adultes, une espèce hibernante inféodée, dans des habitats sources et puits. Nous vérifions l'hypothèse selon laquelle les femelles adultes présenteraient un moins bon embonpoint dans la forêt boréale que dans les baissières adjacentes. Nous avons constaté que, au printemps, les femelles post-partum dans les forêts présentaient une masse (405 ± 7 contre 437 ± 11 g; moyenne ± ET) et un embonpoint (résidue moyenne (±ET) de la masse sur la taille structurale = −11,0 ± 10,2 contre 20,5 ± 6,1 g) inférieurs à ceux des femelles dans les habitats sources de baissière. Cependant, au début de l'entrée en hibernation en août, les spermophiles des forêts avaient atteint la parité avec les spermophiles des baissières et aucune différence de masse (519 ± 13 contre 520 ± 15 g; moyenne ± ET), ni d'embonpoint n'était observée (indice résiduel = −0,01 ± 0,01 contre 0,03 ± 0,01; moyenne ± ET). Nous proposons que, pour les spermophiles dans des forêts boréales occupées antérieurement, (i) le faible embonpoint printanier réduisait le succès de reproduction et (ii) la compensation de la croissance par un approvisionnement accru...

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Managing anabolic steroids in pre-hibernating Arctic ground squirrels: obtaining their benefits and avoiding their costs

Cited by 11 publications

References 15 publications

Hormones do not make the mole-rat: no steroid hormone signatures of subordinate behavioral phenotypes

Hormones do not make the mole-rat: no steroid hormone signatures of subordinate behavioral phenotypes

The influence of androgens on hibernation phenology of free-living male arctic ground squirrels

Forest or meadow: the consequences of habitat for the condition of female arctic ground squirrels (Urocitellus parryii plesius)

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