No abstract

Many species of birds and bats undertake seasonal migrations between breeding and over-wintering sites. En-route, migrants alternate periods of flight with time spent at stopover – the time and space where individuals rest and refuel for subsequent flights. We assessed the spatial scale of movements made by migrants during stopover by using an array of automated telemetry receivers with multiple antennae to track the daily location of individuals over a geographic area ∼20×40 km. We tracked the movements of 322 individuals of seven migratory vertebrate species (5 passerines, 1 owl and 1 bat) during spring and fall migratory stopover on and adjacent to a large lake peninsula. Our results show that many individuals leaving their capture site relocate within the same landscape at some point during stopover, moving as much as 30 km distant from their site of initial capture. We show that many apparent nocturnal departures from stopover sites are not a resumption of migration in the strictest sense, but are instead relocations that represent continued stopover at a broader spatial scale.

An ideal technology for non-invasive analysis of body composition should provide highly precise and accurate direct measurements of fat, lean mass and total water of non-anaesthetized subjects within minutes. We validate a quantitative magnetic resonance (QMR) body composition analyzer for birds using House Sparrows (Passer domesticus), European Starlings (Sturnus vulgaris), and Zebra Finches (Taeniopygia guttata). Subjects were scanned awake for three replicate scans of 1.5-3.5 min, and results were compared to gravimetric chemical analysis. Coefficients of variation were B3% for dry fat, wet lean mass and total water. Accuracy of the raw QMR data for fat and total water were high (relative errors B±12.5 and B±4%, respectively), but wet lean mass was significantly biased because QMR does not detect structural tissues. Calibration against gravimetric chemical analysis removed bias and improved accuracy; relative errors were ±6-11% for fat, ±1-2% for wet lean mass, and ±2-4% for total water. QMR is field-portable when transported in a temperature-controlled trailer, and can be used to study fuel storage and body composition dynamics during migration, reproduction, nestling growth, or wintering. In the laboratory, QMR can be used for longitudinal studies of birds under photoperiod, endocrine or other manipulations. Measurements taken before and after metabolic challenges, such as flight in a wind tunnel, make it possible to calculate energy costs, fuel selection and changes in hydration. QMR should find wide application in field and laboratory studies.

To investigate the effect of hypophyseal transection (HST) on GH secretagogue activity of the non-peptidyl GH secretagogue L-692,585 in the conscious pig, male castrated swine were randomly assigned to either a hypophyseal stalk transection group (HST; n = 3) or to a sham-operated control group (SOC; n = 3). Treatments administered were L-692,585 (100 micrograms/kg), human GH-releasing factor(1-29)NH2 (GRF; 20 micrograms/kg) or L-692,585 (100 micrograms/kg) + GRF (20 micrograms/kg) on days -7 to -3 before surgery and days +3 to +8 after surgery. To evaluate the integrity of the pituitary gland, the animals were challenged with corticotropin-releasing hormone (CRH; 150 micrograms) or GnRH (150 ng/kg) both before and after surgery. Blood was collected from -60 to +180 min post treatment and assayed for GH, cortisol and LH. Before surgery, no significant difference (P > 0.05) in peak GH response (ng/ml) was present between the two groups (SOC vs HST) in response to L-692,585 (101 +/- 12 vs 71 +/- 9) or L-692,585 + GRF (171 +/- 21 vs 174 +/- 21). Only two out of three SOC vs three out of three HST pigs responded to GRF (13 +/- 2 vs 25 +/- 3) resulting in a significant difference between groups. Following surgery, significant differences were present in peak GH response (ng/ml) between SOC and HST groups following L-692,585 (79 +/- 6 vs 13.8 +/- 1.0); however, the response to L-692,585 + GRF was similar (115 +/- 8 vs 94 +/- 7). All animals responded to GRF; however, a significant difference was present between groups due to the magnitude of the responses. Whereas the cortisol responses (ng/ml) to L-692,585 in the SOC and HST groups were similar before surgery, a significant difference was present after surgery (44.4 +/- 6.4 vs 14.6 +/- 2.1). No significant difference was noted between the HST and SOC groups in response to CRH or GnRH either before or after surgery. These results indicated that L-692,585 induced an immediate GH response in the intact animal in contrast to GRF where the GH release was variable. L-692,585 also stimulated an immediate increase in cortisol levels. Transection of the hypophyseal stalk dramatically decreased but did not ablate the GH or cortisol response to L-692,585. Co-administration of L-692,585 + GRF induced an immediate GH response of similar magnitude in the intact and HST animal. We conclude that L-692,585 has a direct but limited action at the level of the pituitary and that an intact hypophyseal stalk is required for a maximal GH and cortisol response. L-692,585 acts with GRF at the level of the pituitary to induce a maximal GH response. These findings suggest that L-692,585 stimulates GH secretion by acting in combination with GRF and interrupting the inhibitory tone of somatostatin on the somatotroph.

Fungal diseases of wildlife typically manifest as superficial skin infections but can have devastating consequences for host physiology and survival. White-nose syndrome (WNS) is a fungal skin disease that has killed millions of hibernating bats in North America since 2007. Infection with the fungus causes bats to rewarm too often during hibernation, but the cause of increased arousal rates remains unknown. On the basis of data from studies of captive and free-living bats, two mechanistic models have been proposed to explain disease processes in WNS. Key predictions of both models are that WNS-affected bats will show) higher metabolic rates during torpor (TMR) and ) higher rates of evaporative water loss (EWL). We collected bats from a WNS-negative hibernaculum, inoculated one group with, and sham-inoculated a second group as controls. After 4 mo of hibernation, TMR and EWL were measured using respirometry. Both predictions were supported, and our data suggest that infected bats were more affected by variation in ambient humidity than controls. Furthermore, disease severity, as indicated by the area of the wing with UV fluorescence, was positively correlated with EWL, but not TMR. Our results provide the first direct evidence that heightened energy expenditure during torpor and higher EWL independently contribute to WNS pathophysiology, with implications for the design of potential treatments for the disease.