Codesigning an E-Health Intervention for Surgery Preparation and Recovery.

Surgery is a significant part of healthcare, but its demand is increasing, leading to challenges in managing patient care. Inefficient perioperative practices and traditional linear models contribute to adverse outcomes and patient anxiety. E-health interventions show promise in improving surgical care, but more research is needed. The purpose of this study was to involve patients and healthcare workers during the design phase of an e-health intervention that aims to support the perioperative care of elective surgery preparation and recovery. This study used an Information Systems Research Framework to guide collaborative codesign through semistructured interviews and cocreation workshops. Semistructured interviews collected insights on the perioperative journey and e-health needs from healthcare workers and consumers, resulting in the creation of a patient surgery journey map, experience map, and a stakeholder needs table. Collaborative work between consumers and healthcare workers in the cocreation workshops identified priority perioperative journey issues and proposed solutions, as well as prioritizing application software needs, guiding the development of the wireframe. The development of an e-health application aimed at supporting surgery preparation and recovery is a significant step toward improving patient engagement, satisfaction, and postsurgical health outcomes.

SAD rats: Effects of short photoperiod and carbohydrate consumption on sleep, liver steatosis, and the gut microbiome in diurnal grass rats.

Seasonal affective disorder (SAD) is a recurrent depression triggered by exposure to short photoperiods, with a subset of patients reporting hypersomnia, increased appetite, and carbohydrate craving. Dysfunction of the microbiota - gut - brain axis is frequently associated with depressive disorders, but its role in SAD is unknown. Nile grass rats (Arvicanthis niloticus) are potentially useful for exploring the pathophysiology of SAD, as they are diurnal and have been found to exhibit anhedonia and affective-like behavior in response to short photoperiods. Further, given grass rats have been found to spontaneously develop metabolic syndrome, they may be particularly susceptible to environmental triggers of metabolic dysbiosis. We conducted a 2 × 2 factorial design experiment to test the effects of short photoperiod (4 h:20 h Light:Dark (LD) vs. neutral 12:12 LD), access to a high concentration (8%) sucrose solution, and the interaction between the two, on activity, sleep, liver steatosis, and the gut microbiome of grass rats. We found that animals on short photoperiods maintained robust diel rhythms and similar subjective day lengths as controls in neutral photoperiods but showed disrupted activity and sleep patterns (i.e. a return to sleep after an initial bout of activity that occurs ~ 13 h before lights off). We found no evidence that photoperiod influenced sucrose consumption. By the end of the experiment, some grass rats were overweight and exhibited signs of non-alcoholic fatty liver disease (NAFLD) with micro- and macro-steatosis. However, neither photoperiod nor access to sucrose solution significantly affected the degree of liver steatosis. The gut microbiome of grass rats varied substantially among individuals, but most variation was attributable to parental effects and the microbiome was unaffected by photoperiod or access to sucrose. Our study indicates short photoperiod leads to disrupted activity and sleep in grass rats but does not impact sucrose consumption or exacerbate metabolic dysbiosis and NAFLD.

Partnering with consumers to co-design a person-centred coding framework for qualitative patient experience data.

BACKGROUND: Patient Reported Experience Measures (PREMs) provide health organisations insight into how 'person-centric' care is. Qualitative data in PREMs surveys provide essential context about experience but are challenging to analyse at an organisational level. OBJECTIVE: To co-design a person-centred coding framework to assist in the analysis of qualitative PREMs data. PATIENT INVOLVEMENT: Consumer representatives were involved in problem identification, co-design, coding of raw data (testing), evaluation and manuscript authorship. METHODOLOGY: Co-design principles guided production of a deductive coding framework with Picker Principles of Person-Centred Care as a conceptual framework. The framework was co-designed over 4 stages, with cross-professional stakeholders (including two consumer representatives): 1) assessment of current state and understanding priorities; 2) adapting Picker Principles of Person-Centred Care as a coding framework; 3) testing and evaluation of a coding template over two quality improvement (QI) cycles against measures of inter-coder reliability and perceived usefulness; 4) endorsement and planning for implementation. RESULTS: The Picker Principles were a suitable coding framework for inpatient PREMs data, and a coding template in an electronic spreadsheet met end-user needs. Results of the first QI cycle indicated a need for 'less academic' domain names and definitions, which were reviewed and updated to a first-person perspective in partnership with a consumer representative. Inter-coder reliability measures and qualitative feedback improved after cycle two testing and evaluation. DISCUSSION: This single site study produced a feasible solution to apply person-centred principles to analyse PREMs data and requires testing in different settings. Cross-disciplinary partnerships enabled the development of a reliable and acceptable deductive coding framework that was usable for people without prior experience in qualitative data analysis. PRACTICAL VALUE: Our solution offers an example for health services to harness the value of qualitative PREMs data and partner with consumers to take person-centric action to improve the safety, equity, and experience of healthcare.

Climate change is altering the physiology and phenology of an arctic hibernator.

Climate warming is rapid in the Arctic, yet impacts to biological systems are unclear because few long-term studies linking biophysiological processes with environmental conditions exist for this data-poor region. In our study spanning 25 years in the Alaskan Arctic, we demonstrate that climate change is affecting the timing of freeze-thaw cycles in the active layer of permafrost soils and altering the physiology of arctic ground squirrels (Urocitellus parryii). Soil freeze has been delayed and, in response, arctic ground squirrels have delayed when they up-regulate heat production during torpor to prevent freezing. Further, the termination of hibernation in spring has advanced 4 days per decade in females but not males. Continued warming and phenological shifts will alter hibernation energetics, change the seasonal availability of this important prey species, and potentially disrupt intraspecific interactions.

TDFCAM: A method for estimating stable isotope trophic discrimination in wild populations.

Stable isotope mixing models (SIMMs) are widely used for characterizing wild animal diets. Such models rely upon using accurate trophic discrimination factors (TDFs) to account for the digestion, incorporation, and assimilation of food. Existing methods to calculate TDFs rely on controlled feeding trials that are time-consuming, often impractical for the study taxon, and may not reflect natural variability of TDFs present in wild populations.We present TDFCAM as an alternative approach to estimating TDFs in wild populations, by using high-precision diet estimates from a secondary methodological source-in this case nest cameras-in lieu of controlled feeding trials, and provide a framework for how and when it should be applied.In this study, we evaluate the TDFCAM approach in three datasets gathered on wild raptor nestlings (gyrfalcons Falco rusticolus; peregrine falcons Falco perigrinus; common buzzards Buteo buteo) comprising contemporaneous δ13C & δ15N stable isotope data and high-quality nest camera dietary data. We formulate Bayesian SIMMs (BSIMMs) incorporating TDFs from TDFCAM and analyze their agreement with nest camera data, comparing model performance with those based on other relevant TDFs. Additionally, we perform sensitivity analyses to characterize TDFCAM variability, and identify ecological and physiological factors contributing to that variability in wild populations.Across species and tissue types, BSIMMs incorporating a TDFCAM outperformed any other TDF tested, producing reliable population-level estimates of diet composition. We demonstrate that applying this approach even with a relatively low sample size (n < 10 individuals) produced more accurate estimates of trophic discrimination than a controlled feeding study conducted on the same species. Between-individual variability in TDFCAM estimates for ∆13C & ∆15 N increased with analytical imprecision in the source dietary data (nest cameras) but was also explained by natural variables in the study population (e.g., nestling nutritional/growth status and dietary composition).TDFCAM is an effective method of estimating trophic discrimination in wild animal populations. Here, we use nest cameras as source dietary data, but this approach is applicable to any high-accuracy method of measuring diet, so long as diet can be monitored over an interval contemporaneous with a tissue's isotopic turnover rate.

Effects of Spring Warming on Seasonal Neuroendocrinology and Activation of the Reproductive Axis in Hibernating Arctic Ground Squirrels.

Many animals adjust the timing of seasonal events, such as reproduction, molt, migration, and hibernation, in response to interannual variation and directional climate-driven changes in temperature. However, the mechanisms by which temperature influences seasonal timing are relatively under-explored. Seasonal timing involves retrograde signaling in which thyrotropin (TSH) in the pars tuberalis (PT) alters expression of thyroid hormone (TH) deiodinases (Dio2/Dio3) in tanycyte cells lining the third ventricle of the hypothalamus. This, in turn, affects the availability of triiodothyronine (T3) within the mediobasal hypothalamus-increased hypothalamic T3 restores a summer phenotype and activates the reproductive axis in long-day breeders. Recently, we showed that retrograde TH signaling is activated during late hibernation in arctic ground squirrels (Urocitellus parryii) held in constant darkness and constant ambient temperature. Sensitivity of seasonal pathways to nonphotic cues, such as temperature, is likely particularly important to hibernating species that are sequestered in hibernacula during spring. To address this issue, we exposed captive arctic ground squirrels of both sexes to an ecologically relevant increase in ambient temperature (from -6 to -1°C) late in hibernation and examined the effects of warming on the seasonal retrograde TSH/Dio/T3 signaling pathway, as well as downstream elements of the reproductive axis. We found that warmed males tended to have higher PT TSHß expression and significantly heavier testis mass whereas the TSH/Dio/T3 signaling pathway was unaffected by warming in females, although warmed females exhibited a slight decrease in ovarian mass. Our findings suggest that temperature could have different effects on gonadal growth in male and female arctic ground squirrels, which could lead to mismatched timing in response to rapid climate change.

Vertebrate Phenological Plasticity: From Molecular Mechanisms to Ecological and Evolutionary Implications.

Seasonal variation in the availability of essential resources is one of the most important drivers of natural selection on the phasing and duration of annually recurring life-cycle events. Shifts in seasonal timing are among the most commonly reported responses to climate change and the capacity of organisms to adjust their timing, either through phenotypic plasticity or evolution, is a critical component of resilience. Despite growing interest in documenting and forecasting the impacts of climate change on phenology, our ability to predict how individuals, populations, and species might alter their seasonal timing in response to their changing environments is constrained by limited knowledge regarding the cues animals use to adjust timing, the endogenous genetic and molecular mechanisms that transduce cues into neural and endocrine signals, and the inherent capacity of animals to alter their timing and phasing within annual cycles. Further, the fitness consequences of phenological responses are often due to biotic interactions within and across trophic levels, rather than being simple outcomes of responses to changes in the abiotic environment. Here, we review the current state of knowledge regarding the mechanisms that control seasonal timing in vertebrates, as well as the ecological and evolutionary consequences of individual, population, and species-level variation in phenological responsiveness. Understanding the causes and consequences of climate-driven phenological shifts requires combining ecological, evolutionary, and mechanistic approaches at individual, populational, and community scales. Thus, to make progress in forecasting phenological responses and demographic consequences, we need to further develop interdisciplinary networks focused on climate change science.

A cross-taxonomic perspective on the integration of temperature cues in vertebrate seasonal neuroendocrine pathways.

The regulation of seasonality has been an area of interest for decades, yet global climate change has created extra urgency in the quest to understand how sensory circuits and neuroendocrine control systems interact to generate flexibility in biological timekeeping. The capacity of temperature to alter endogenous or photoperiod-regulated neuroendocrine mechanisms driving seasonality, either as a direct cue or through temperature-dependent effects on energy and metabolism, is at the heart of this phenological flexibility. However, until relatively recently, little research had been done on the integration of temperature information in canonical seasonal neuroendocrine pathways, particularly in vertebrates. We review recent advances from research in vertebrates that deepens our understanding of how temperature cues are perceived and integrated into seasonal hypothalamic thyroid hormone (TH) signaling, which is a critical regulator of downstream seasonal phenotypic changes such as those regulated by the BPG (brain-pituitary-gonadal) axis. Temperature perception occurs through cutaneous transient receptor potential (TRP) neurons, though sensitivity of these neurons varies markedly across taxa. Although photoperiod is the dominant cue used to trigger seasonal physiology or entrain circannual clocks, across birds, mammals, fish, reptiles and amphibians, seasonality appears to be temperature sensitive and in at least some cases this appears to be related to phylogenetically conserved TH signaling in the hypothalamus. Nevertheless, the exact mechanisms through which temperature modulates seasonal neuroendocrine pathways remains poorly understood.

Sex-Differences in Phenology: A Tinbergian Perspective.

Shifts in the timing of cyclic seasonal life-history events are among the most commonly reported responses to climate change, with differences in response rates among interacting species leading to phenological mismatches. Within a species, however, males and females can also exhibit differential sensitivity to environmental cues and may, therefore, differ in their responsiveness to climate change, potentially leading to phenological mismatches between the sexes. This occurs because males differ from females in when and how energy is allocated to reproduction, resulting in marked sex-differences in life-history timing across the annual cycle. In this review, we take a Tinbergian perspective and examine sex-differences in timing of vertebrates from adaptive, ontogenetic, mechanistic, and phylogenetic viewpoints with the goal of informing and motivating more integrative research on sexually dimorphic phenologies. We argue that sexual and natural selection lead to sex-differences in life-history timing and that understanding the ecological and evolutionary drivers of these differences is critical for connecting climate-driven phenological shifts to population resilience. Ontogeny may influence how and when sex-differences in life-history timing arise because the early-life environment can profoundly affect developmental trajectory, rates of reproductive maturation, and seasonal timing. The molecular mechanisms underlying these organismal traits are relevant to identifying the diversity and genetic basis of population- and species-level responses to climate change, and promisingly, the molecular basis of phenology is becoming increasingly well-understood. However, because most studies focus on a single sex, the causes of sex-differences in phenology critical to population resilience often remain unclear. New sequencing tools and analyses informed by phylogeny may help generate hypotheses about mechanism as well as insight into the general "evolvability" of sex-differences across phylogenetic scales, especially as trait and genome resources grow. We recommend that greater attention be placed on determining sex-differences in timing mechanisms and monitoring climate change responses in both sexes, and we discuss how new tools may provide key insights into sex-differences in phenology from all four Tinbergian domains.

Hypothalamic remodeling of thyroid hormone signaling during hibernation in the arctic ground squirrel.

Hibernation involves prolonged intervals of profound metabolic suppression periodically interrupted by brief arousals to euthermy, the function of which is unknown. Annual cycles in mammals are timed by a photoperiodically-regulated thyroid-hormone-dependent mechanism in hypothalamic tanycytes, driven by thyrotropin (TSH) in the pars tuberalis (PT), which regulates local TH-converting deiodinases and triggers remodeling of neuroendocrine pathways. We demonstrate that over the course of hibernation in continuous darkness, arctic ground squirrels (Urocitellus parryii) up-regulate the retrograde TSH/Deiodinase/TH pathway, remodel hypothalamic tanycytes, and activate the reproductive axis. Forcing the premature termination of hibernation by warming animals induced hypothalamic deiodinase expression and the accumulation of secretory granules in PT thyrotrophs and pituitary gonadotrophs, but did not further activate the reproductive axis. We suggest that periodic arousals may allow for the transient activation of hypothalamic thyroid hormone signaling, cellular remodeling, and re-programming of brain circuits in preparation for the short Arctic summer.

Isotopic niche partitioning and individual specialization in an Arctic raptor guild.

Intra- and inter-specific resource partitioning within predator communities is a fundamental component of trophic ecology, and one proposed mechanism for how populations partition resources is through individual niche variation. The Niche Variation Hypothesis (NVH) predicts that inter-individual trait variation leads to functional trade-offs in foraging efficiency, resulting in populations composed of individual dietary specialists. The degree to which niche specialization persists within a population is plastic and responsive to fluctuating resource availability. We quantified niche overlap and tested the NVH within an Arctic raptor guild, focusing on three species that employ different foraging strategies: golden eagles (generalists); gyrfalcons (facultative specialists); and rough-legged hawks (specialists). Tundra ecosystems exhibit cyclic populations of arvicoline rodents (lemmings and voles), providing a unique system in which to examine predator diet in response to interannual fluctuations in resource availability. Using blood δ13C and δ15N values from 189 raptor nestlings on Alaska's Seward Peninsula (2014-2019), we calculated isotopic niche width and used Bayesian stable isotope mixing models (BSIMMs) to characterize individual specialization and test the NVH. Nest-level specialization estimated from stable isotopes was strongly correlated with indices of specialization based on camera trap data. We observed a high degree of isotopic niche overlap between the three species and gyrfalcons displayed a positive relationship between individual specialization and population niche width on an interannual basis consistent with the NVH. Our findings suggest plasticity in niche specialization may reduce intra- and inter-specific resource competition under dynamic ecological conditions.

The darkness and the light: diurnal rodent models for seasonal affective disorder.

The development of animal models is a critical step for exploring the underlying pathophysiological mechanisms of major affective disorders and for evaluating potential therapeutic approaches. Although most neuropsychiatric research is performed on nocturnal rodents, differences in how diurnal and nocturnal animals respond to changing photoperiods, combined with a possible link between circadian rhythm disruption and affective disorders, has led to a call for the development of diurnal animal models. The need for diurnal models is most clear for seasonal affective disorder (SAD), a widespread recurrent depressive disorder that is linked to exposure to short photoperiods. Here, we briefly review what is known regarding the etiology of SAD and then examine progress in developing appropriate diurnal rodent models. Although circadian disruption is often invoked as a key contributor to SAD, a mechanistic understanding of how misalignment between endogenous circadian physiology and daily environmental rhythms affects mood is lacking. Diurnal rodents show promise as models of SAD, as changes in affective-like behaviors are induced in response to short photoperiods or dim-light conditions, and symptoms can be ameliorated by brief exposure to intervals of bright light coincident with activity onset. One exciting avenue of research involves the orexinergic system, which regulates functions that are disturbed in SAD, including sleep cycles, the reward system, feeding behavior, monoaminergic neurotransmission and hippocampal neurogenesis. However, although diurnal models make intuitive sense for the study of SAD and are more likely to mimic circadian disruption, their utility is currently hampered by a lack of genomic resources needed for the molecular interrogation of potential mechanisms.

Thermoregulation in hibernating mammals: The role of the "thyroid hormones system".

Hibernation is a unique evolutionary adaptation to conserve energy. During the pre-hibernation (i.e. fall) season, a progressive decline in core body temperature and further decrease in metabolism underlie a seasonal modulation in thermoregulation. The onset of hibernation requires marked changes in thermoregulatory attributes including adjustment in body temperature and tissue specific increases in thermogenic capacity. The hibernation season is characterized by a regulated suppression in thermogenesis allowing the onset of torpor interrupted by periodic activation of thermogenesis to sustain interbout arousals. Thyroid hormones are known to regulate both body temperature and metabolism, and for this reason, the hypothalamic-pituitary-thyroid axis and thyroid hormones have been investigated as modulators of thermogenesis in the phenomenon of hibernation, but the mechanisms remain poorly understood. In this review, we present an overview of what is known about the thermogenic roles of thyroid hormones in hibernating species across seasons and within the hibernating season (torpor-interbout arousal cycle). Overall, the hypothalamic-pituitary-thyroid axis and thyroid hormones play a role in the pre-hibernation season to enhance thermogenic capacity. During hibernation, thermogenesis is attenuated at the level of sympathetic premotor neurons within the raphe pallidus and by deiodinase expression in the hypothalamus. Further, as recent work highlights the direct effect of thyroid hormones within the central nervous system in activating thermogenesis, we speculate how similar mechanisms may occur in hibernating species to modulate thermogenesis across seasons and to sustain interbout arousals. However, further experiments are needed to elucidate the role of thyroid hormones in hibernation, moving towards the understanding that thyroid hormones metabolism, transport and availability within tissues may be the most telling indicator of thyroid status.

Bayesian stable isotope mixing models effectively characterize the diet of an Arctic raptor.

Bayesian stable isotope mixing models (BSIMMs) for δ13 C and δ15 N can be a useful tool to reconstruct diets, characterize trophic relationships, and assess spatiotemporal variation in food webs. However, use of this approach typically requires a priori knowledge on the level of enrichment occurring between the diet and tissue of the consumer being sampled (i.e. a trophic discrimination factor or TDF). Trophic discrimination factors derived from captive feeding studies are highly variable, and it is challenging to select the appropriate TDF for diet estimation in wild populations. We introduce a novel method for estimating TDFs in a wild population-a proportionally balanced equation that uses high-precision diet estimates from nest cameras installed on a subset of nests in lieu of a controlled feeding study (TDFCAM ). We tested the ability of BSIMMs to characterize diet in a free-living population of gyrfalcon Falco rusticolus nestlings by comparing model output to high-precision nest camera diet estimates. We analysed the performance of models formulated with a TDFCAM against other relevant TDFs and assessed model sensitivity to an informative prior. We applied the most parsimonious model inputs to a larger sample to analyse broad-scale temporal dietary trends. Bayesian stable isotope mixing models fitted with a TDFCAM and uninformative prior had the best agreement with nest camera data, outperforming TDFs derived from captive feeding studies. BSIMMs produced with a TDFCAM produced reliable diet estimates at the nest level and accurately identified significant temporal shifts in gyrfalcon diet within and between years. Our method of TDF estimation produced more accurate estimates of TDFs in a wild population than traditional approaches, consequently improving BSIMM diet estimates. We demonstrate how BSIMMs can complement a high-precision diet study by expanding its spatiotemporal scope of inference and recommend this integrative methodology as a powerful tool for future trophic studies.

Glucocorticoids and activity in free-living arctic ground squirrels: Interrelationships between weather, body condition, and reproduction.

The dynamic relationship between glucocorticoids and behavior are not well understood in wild mammals. We investigated how weather, body condition, and reproduction interact to affect cortisol levels and activity patterns in a free-living population of arctic ground squirrels (Urocitellus parryii). As a proxy for foraging and escape behaviors, collar-mounted accelerometers and light loggers were used to measure above-ground activity levels and the amount of time squirrels spent below the surface, respectively. Fecal cortisol metabolites (FCMs) were quantified to assess glucocorticoid secretion in squirrels. Male and female squirrels differed in above-ground activity levels and time spent below-ground across the active season, with males being most active during mating and females most active during lactation. We also found that female, but not male, squirrels exhibited seasonal variation in FCM levels, with concentrations highest during mid-lactation and lowest after the lactation period. In female squirrels, the seasonal relationships between breeding stage, activity, and FCM levels were also consistent with changes in maternal investment and the preparative role that glucocorticoids are hypothesized to play in energy mobilization. Body condition was not associated with FCM levels in squirrels. As predicted, deteriorating weather also influenced FCM levels and activity patterns in squirrels. FCM concentrations were affected by an interaction between temperature and wind speed when seasonal temperatures were lowest. In addition, above-ground activity, but not time spent below-ground, positively correlated with FCM levels. These results suggest that, although ground squirrels avoid inclement weather by remaining below-ground, activation of the stress axis may stimulate foraging activity.

The Association of Loneliness and Non-prescribed Opioid Use in Patients With Opioid Use Disorder.

OBJECTIVE: To investigate the relationship between loneliness and non-prescribed opioid use in patients diagnosed with opioid use disorder (OUD). METHODS: This was a cohort study conducted at a federally qualified health center (FQHC) in New Haven, CT. Patients who were treated for OUD by health center providers and prescribed buprenorphine were eligible. Participants were asked to complete the UCLA-Loneliness Scale Version 3. From the electronic medical record, we collected patient demographic and clinical characteristics as well as the results of biological fluid testing obtained throughout their treatment course since entry into care. Multivariable logistic regression was performed to identify independent predictors of the detection of non-prescribed opioids within biological fluid. RESULTS: Of the 82 patients enrolled in the study, 33 (40.3%) of the participants had at least 1 biological fluid test positive for non-prescribed opioids after maintenance onto buprenorphine treatment. A higher loneliness score was associated with increased odds of non-prescribed opioids (adjusted odds ratio 1.16; 95% confidence interval 1.06-1.27). Patient age, the number of problems on the problems list, and cocaine use were also positively associated with the presence of non-prescribed opioids whereas having diabetes was negatively associated. CONCLUSIONS: Among the individuals being treated with buprenorphine for OUD, loneliness may be a risk factor for the use of non-prescribed opioids or treatment failure.

Tissue-specific telomere dynamics in hibernating arctic ground squirrels (Urocitellus parryii).

Hibernation is used by a variety of mammals to survive seasonal periods of resource scarcity. Reactive oxygen species (ROS) released during periodic rewarming throughout hibernation, however, may induce oxidative damage in some tissues. Telomeres, which are the terminal sequences of linear chromosomes, may shorten in the presence of ROS, and thus the telomere length of an individual reflects the degree of accrued oxidative damage. This study quantified telomere length dynamics throughout hibernation in arctic ground squirrels (Urocitellus parryii). We hypothesized that telomere dynamics are tissue specific and predicted that telomere shortening would be most pronounced in brown adipose tissue (BAT), the organ that directly supports non-shivering thermogenesis during arousals. We used qPCR to determine relative telomere length (RTL) in DNA extracted from liver, heart, skeletal muscle (SM) and BAT of 45 juvenile and adult animals sampled either at mid- or late hibernation. Age did not have a significant effect on RTL in any tissue. At mid-hibernation, RTL of juvenile females was longer in BAT and SM than in liver and heart. In juvenile females, RTL in BAT and SM, but not in liver and heart, was shorter at late hibernation than at mid-hibernation. At late hibernation, juvenile males had longer RTL in BAT than did juvenile females, perhaps due to the naturally shorter hibernation duration of male arctic ground squirrels. Finally, BAT RTL at late hibernation negatively correlated with arousal frequency. Overall, our results suggest that, in a hibernating mammal, telomere shortening is tissue specific and that metabolically active tissues might incur higher levels of molecular damage.

Is biasing offspring sex ratio adaptive? A test of Fisher's principle across multiple generations of a wild mammal in a fluctuating environment.

Fisher's principle explains that population sex ratio in sexually reproducing organisms is maintained at 1 : 1 owing to negative frequency-dependent selection, such that individuals of the rare sex realize greater reproductive opportunity than individuals of the more common sex until equilibrium is reached. If biasing offspring sex ratio towards the rare sex is adaptive, individuals that do so should have more grandoffspring. In a wild population of North American red squirrels (Tamiasciurus hudsonicus) that experiences fluctuations in resource abundance and population density, we show that overall across 26 years, the secondary sex ratio was 1 : 1; however, stretches of years during which adult sex ratio was biased did not yield offspring sex ratios biased towards the rare sex. Females that had litters biased towards the rare sex did not have more grandoffspring. Critically, the adult sex ratio was not temporally autocorrelated across years, thus the population sex ratio experienced by parents was independent of the population sex ratio experienced by their offspring at their primiparity. Expected fitness benefits of biasing offspring sex ratio may be masked or negated by fluctuating environments across years, which limit the predictive value of the current sex ratio.

Phenological shifts in North American red squirrels: disentangling the roles of phenotypic plasticity and microevolution.

Phenological shifts are the most widely reported ecological responses to climate change, but the requirements to distinguish their causes (i.e. phenotypic plasticity vs. microevolution) are rarely met. To do so, we analysed almost two decades of parturition data from a wild population of North American red squirrels (Tamiasciurus hudsonicus). Although an observed advance in parturition date during the first decade provided putative support for climate change-driven microevolution, a closer look revealed a more complex pattern. Parturition date was heritable [h2  = 0.14 (0.07-0.21 (HPD interval)] and under phenotypic selection [ß = -0.14 ± 0.06 (SE)] across the full study duration. However, the early advance reversed in the second decade. Further, selection did not act on the genetic contribution to variation in parturition date, and observed changes in predicted breeding values did not exceed those expected due to genetic drift. Instead, individuals responded plastically to environmental variation, and high food [white spruce (Picea glauca) seed] production in the first decade appears to have produced a plastic advance. In addition, there was little evidence of climate change affecting the advance, as there was neither a significant influence of spring temperature on parturition date or evidence of a change in spring temperatures across the study duration. Heritable traits not responding to selection in accordance with quantitative genetic predictions have long presented a puzzle to evolutionary ecologists. Our results on red squirrels provide empirical support for one potential solution: phenotypic selection arising from an environmental, as opposed to genetic, covariance between the phenotypic trait and annual fitness.