Biology subjects

Hambly, C.

Publications and source records attributed to Hambly, C..

3 recordsLinked to original sources

bioRxiv2023

Validating Dynamic Body Acceleration metrics as a measure of energy expenditure in a Neotropical primate

2AO_SCPLOWBSTRACTC_SCPLOWQuantifying energy expenditure in free-living primates is fundamentally important yet challenging. Acceleration-based metrics such as Dynamic Body Acceleration (DBA), obtained from accelerometers, are potential proxies for energy expenditure, yet have not been previously validated in primates. Here, we validated DBA in black lion tamarins (Leontopithecus chrysopygus) by comparison to doubly labelled water (DLW) in 10 captive tamarins housed at the Rio de Janeiro Primate Centre. Individuals were equipped over 48 hours with a backpack with a tri-axial accelerometer and received an intra-peritoneal DLW injection at the beginning of the experiment, with blood samples taken 1 and 48h later. Daily Energy Expenditure by DLW was 326 (SD=66) kJ/day, close to expected values for primates of their size. The accelerometers recorded at 40 Hz, collecting >6.9 million records per axis for each individual. Individual DBA metrics were calculated and regressed against DLW daily energy measures. From this regression, we found a consistent and significant linear relationship (R2 = 0.46) between DLW and DBA, which could be improved by the incorporation of activity and resting time information (R2 = 0.52). Our results provide the first estimates of total daily energy expenditure for black lion tamarins and a validation of the method for estimating energy expenditure through accelerometers. Given the similar levels of total energy expenditure of captive and wild primates, this method can now be used in the field to estimate the energy cost of black lion tamarin movements in its natural environment. 1 SO_SCPLOWUMMARYC_SCPLOWO_SCPCAP C_SCPCAPO_SCPLOWSTATEMENTC_SCPLOWDynamic body acceleration was validated against doubly labelled water in black lion tamarins, showing it is a useful tool for measuring free-living energy demands.

zoology↗

bioRxiv2023

Seasonal variation in great tit (Parus major) energy requirements: reallocation versus increased demand

Understanding how birds annually allocate energy to cope with changing environmental conditions and physiological states is a fundamental question in avian ecology. The two main hypotheses to explain annual patterns in energy use are "reallocation" and "increased demand". The reallocation hypothesis suggests equal energetic costs in winter and breeding seasons, while the increased demand suggests that energy demand should be highest during breeding. Under the standard aerobic capacity model of endothermy, birds are expected to adjust the mass and/or metabolic intensity of their bodies in ways that are consistent with expected cold- and/or activity-induced costs. Here, we look for metabolic signatures of reallocation versus increased demands in the energy requirements of a small, resident passerine of a temperate-zone (great tit, Parus major). To do so, we measured whole-body and mass-independent basal (BMR), summit (Msum), and field (FMR) metabolic rates during late winter and during the chick-rearing period (breeding). We also assessed whether, and to what extent, metabolic rates conform to the predictions of the aerobic capacity model of endothermy. We found that great tits showed no substantial differences in energy expenditure between winter and the breeding season, providing support for the reallocation hypothesis. Only mass-independent Msum showed seasonal variation, with significantly higher values ([~]4%) in winter compared to the breeding season. Our results also lend support to the predictions of the aerobic capacity model for the evolution of endothermy, as we found that whole-body BMR and Msum were positively related. We argue that both energy reallocation and the limited increase in mass-independent Msum are consistent with the relatively mild winter temperatures recorded during our study period. Our results confirm that both BMR and Msum are flexible traits that vary in ways that are consistent with expected cold- and/or activity-induced costs.

ecology↗

bioRxiv2020

A mesocosm experiment in ecological physiology: adaptive modulation of energy budget in a hibernating marsupial under chronic caloric restriction

During the last sixty years, mammalian hibernation (i.e., seasonal torpor) has been interpreted as a physiological adaptation for energy economy. However -and crucially for validating this idea - direct field comparisons of energy expenditure in hibernating and active free-ranging animals are scarce. Using replicated mesocosms and a combination of energy budgeting approaches (i.e., doubly labelled water, rates of CO2 production and food intake), we experimentally manipulated energy availability and quantified net energy costs of hibernation in a marsupial. We hypothesized that, when facing chronic caloric restriction (CCR), a hibernator should maximize torpor use for compensating the energetic deficit, compared to ad libitum fed individuals (=controls). However, intensifying torpor duration at low temperatures could increase other burdens (e.g., cost of rewarming, freezing risk). In order to explore this trade-off, we followed the complete hibernation cycle of the relict marsupial Dromiciops gliroides, and estimated its total energy requirements, and compared this with a control condition. Our results revealed: (1) that energy restricted animals, instead of promoting heat conservation strategies during hibernation (e.g., social clustering and thermoregulation), maximized torpor use and saved just enough energy to cover the deficit, and (2) that hibernation represents a net energy saving of 51% compared with animals that remained active. This work provides compelling evidence of a fine-tuning use of hibernation in response to food availability and presents the first direct estimation of energy savings by hibernation encompassing the total hibernation cycle.

ecology↗