Hormonal correlations at transition from reproduction to molting in an annual life cycle of Humboldt penguins (Spheniscus humboldti)

Fecal glucocorticoid analysis as a health monitoring tool for endangered African penguins (Spheniscus demersus)

African penguins (Spheniscus demersus) are an endangered species, with approximately 70,000 mature adults remaining in the wild. Population loss is linked to a combination of environmental and anthropogenic stressors. The aim of the study was to validate a commercially available enzyme immunoassay (EIA) to assess adrenal activity and measure the response to stressors in the feces of African penguins. Fecal samples (n = 609) were collected from 12 African penguins housed at Mystic Aquarium throughout their natural lifecycle, including breeding and molt, where measurable changes in fecal glucocorticoid metabolite (FGM) levels are predicted to occur. Fecal samples collected post-veterinary exam were used for biological validation. Longitudinal analysis shows a significant difference (p = <0.0001) between the average FGM levels during baseline and breeding season, 33.97 ± 1.30 ng/g and 50.21 ± 3.18 ng/g, respectively. Females displayed significantly higher FGM levels than males during both baseline (p = 0.0386; females = 38.80 ± 2.19 ng/g; males = 29.34 ± 1.37 ng/g) and breeding periods (p = 0.0175; females = 57.53 ± 4.84 ng/g; males = 42.69 ± 3.95 ng/g). Average FGM levels decreased significantly over the three-week molting period, from 85.40 ± 20.35 ng/g at week one to 20.23 ± 5.30 ng/g at week three. A seasonal difference in FGM levels was observed in both male and female fecal samples, with Fall having the highest average FGM levels, 54.38 ± 3.64 ng/g, and Summer the lowest, 30.87 ± 2.21 ng/g. General linear mixed model analysis determined that lifecycle (females) and visitor presence (males) were the two factors which best explained the variation in FGM levels observed, however neither factor was found to be significant. These results show FGM analysis can detect physiologically meaningful changes in endocrine activity in African penguins and can be used to monitor health for penguins in aquaria and in the wild, thus contributing to conservation efforts for the survival of the species.

Determination of Annual Plasma Hormone Levels Associated with Reproduction in Long-Day Breeding Domestic Geese

Simple Summary

In domestic birds, breeding practices and optimisation of the microenviroment and nutrition ensure egg production throughout the entire year. However, domestic geese experience an annual cycle of reproductive quiescence and recrudescence. Thus, patterns of reproductive hormones related to the initiation and termination of the breeding–laying period between the sexes seems to be especially important. This paper presents annual patterns of prolactin (PRL), triiodothyronine (T3), thyroxine (T4), testosterone (T), progesterone (P4), and estradiol (E2) in ganders and female geese. Long-day breeding Zatorska geese kept in controlled commercial conditions experienced periods with elevated plasma PRL levels in both sexes post-breeding and during the second half of the breeding–laying period. Increased plasma PRL levels by the end of the breeding–laying period were detected earlier in ganders than in female geese. Annual patterns of thyroid hormones (THs) were partially in agreement with existing theories on the specific role of THs in termination of breeding, which is permissive rather than causal. It may be suggested that ganders terminate their breeding–laying period one month earlier than female geese. These results may be useful in the manipulation of the endocrine axis to extend the duration of seasonal hatching egg production.

Abstract

This paper examines the dynamics of circulating hormone changes connected with reproduction in geese during the annual period related to gonad morphometry. One hundred geese were examined. The levels of prolactin (PRL), triiodothyronine (T3), thyroxine (T4), testosterone (T), progesterone (P4) and estradiol (E2) were estimated. In both sexes, PRL level patterns fit a quadratic trend with elevations in the post-breeding and the second half of the breeding–laying periods. During these periods, differences in the PRL level between sexes were noted. In ganders, increased PRL levels during the laying period occurred earlier compared to in female geese. Cubic trends for T and E2 in ganders and quadratic for T, P4, and E2 in female geese were observed. PRL was negatively correlated with T in both sexes and with P4 and E2 in female geese. A higher level of T3 and variation in T4 in ganders with a quartic trend in ganders vs. a quadratic in female geese were noted. Patterns of PRL, T, and E2 suggested that the breeding–laying period in ganders may be shorter than in female geese. These findings will be used to explore experimental manipulations of the endocrine axis to increase synchronisation of both sexes.

Consequences of phenological shifts and a compressed breeding period in Magellanic penguins

Phenological shifts may ameliorate negative effects of climate change or create carryover effects and mismatches that decrease fitness. Identifying how phenological shifts affect performance is critical for understanding how individuals and populations will respond to climate change, but requires long-term, longitudinal data. Using 34 yr of data from the Magellanic penguin (Spheniscus magellanicus) colony at Punta Tombo, Argentina, we examined the consequences of the delayed onset of breeding (i.e., arrival and egg-laying dates) that has occurred at the colony since 1983. To understand how the delay propagates through the rest of the reproductive cycle, we identified phenological trends in hatch and fledge dates. Median hatch dates were 0.29 d later each year, amounting to a 10-d shift over the course of the study. Median fledge dates did not shift over the 34-yr period, however, thus shortening the median nestling period duration by 14%. We tested several predictions regarding performance outcomes of the compressed nestling period, finding that later-hatched chicks fledged significantly younger than earlier-hatched chicks, and that younger fledglings left the colony with smaller bills and with more chick down. Interestingly, although younger chicks fledged significantly lighter and in worse body condition than older fledglings early in the study, this trend reversed over time, with younger chicks actually fledging heavier and in better body condition in more recent years. Smaller and lighter fledglings were less likely to recruit to the colony as adults. We find that delayed breeding has significantly compressed nestling periods at Punta Tombo, influencing chick growth and fledgling condition. These findings highlight the importance of studying phenology across multiple life events to understand the consequences of phenological shifts for organismal fitness.

FACTORS AFFECTING ABNORMAL MOLTING IN THE MANAGED AFRICAN PENGUIN (SPHENISCUS DEMERSUS) POPULATION IN NORTH AMERICA

Abnormal molting, including partial or incomplete molt, arrested molt cycle, or inappropriate frequency of molt, is a primary concern for the managed African penguin (Spheniscus demersus) population and is documented across institutions. To identify factors associated with increased odds of abnormal molts and characterize intervention opportunities, a comprehensive survey evaluating numerous husbandry and medical parameters was created. Survey results represent 45 North American African penguin holding facilities and 736 unique animals. Of these individuals, 135 (18.3%) demonstrated an abnormal molt over the 5-yr study period (2012-2017). Increased odds ratios for abnormal molt included biologic (age, sex, etc.), geographic (elevation, latitude), and husbandry (exhibit design, diet, etc.) variables. The mean age of affected animals was 15.2 yr (1-45 yr, n = 135) compared with 9.92 yr (4 mo-38 yr, n = 601) for unaffected animals. In addition, although statistically insignificant, males were overrepresented in the affected cohort compared with a near even distribution among unaffected animals. Identified factors with increased odds for abnormal molting included advanced age and facilities using freshwater pools. Normally molting penguins were more commonly found with saltwater pool access and natural lighting exposure. Anecdotal medical intervention attempts are discussed, although further research is needed to define their use. Of attempted interventions, subcutaneous 5.4-mg melatonin implants placed in anticipation of environmental molting cues showed the most promise at inducing catastrophic molt, with 14 of 17 (82.3%) of affected individuals molting normally following this treatment. Survey analysis indicated that abnormal molt is a complex, multifactorial process, and modifiable factors that may predispose animals to abnormally molt exist. Addressing these factors in future exhibit design may mitigate the prevalence of this condition. Despite these efforts, it is likely that medical interventions will be required to aid in the treatment of abnormal molting in this species.

Behavioral responses of beluga whales (Delphinapterus leucas) to environmental variation in an Arctic estuary

Some Arctic estuaries serve as substrate rubbing sites for beluga whales (Delphinapterus leucas) in the summer, representing a specialized resource for the species. Understanding how environmental variation affects the species' behavior is essential to management of these habitats in coming years as the climate changes. Spatiotemporal and environmental variables were recorded for behavioral observations, during which focal groups of whales in an estuary were video-recorded for enumeration and behavioral analysis. Multiple polynomial linear regression models were optimized to identify the effects of spatiotemporal and environmental conditions on group size, composition, and the frequency of behaviors being performed. Results suggest that belugas take advantage of environmental variation to express behaviors that 1) protect young, e.g., bringing calves close to shore during cloudier days, obscuring visualization from terrestrial predators; 2) avoid predation, e.g., rubbing against substrates at higher Beaufort sea states to obscure visualization, and resting during low tides while swimming on outgoing tides to avoid stranding; and 3) optimize bioenergetic resources, e.g., swimming during lower Beaufort sea states and clearer days. Predictive models like the ones presented in this study can inform conservation management strategies as environmental conditions change in future years.

FORCED MOLT IN FOUR JUVENILE YELLOW-EYED PENGUINS (MEGADYPTES ANTIPODES)

Penguins are dependent on waterproof plumage for survival. The molt in sub-Antarctic penguin species is a seasonal and catastrophic process during which the animals go through periods of fasting and high levels of stress. Their entire plumage is usually replaced in 3 wk. Attempts at consistent hormonal induction of molt in penguins have been unsuccessful. Four Yellow-eyed Penguins ( Megadyptes antipodes ) were referred for treatment at Wildbase, Massey University, Palmerston North, New Zealand, in late April 2014, following loss of waterproofing, feather breakage, increased body weight, pododermatitis, and damage to caudal feathers from hock sitting. Feather plucking of damaged areas to stimulate feather regrowth was attempted with poor results. Waiting 10-12 mo for a natural molt was not tenable. Catastrophic molt was induced by treatment with 10 g/kg of fresh beef thyroid gland orally once a day. The molt was complete in 18-26 d during which the animals regained full plumage and waterproofing after feather regrowth. The forced molt feathers had abnormal pigmentation but were of sufficient quality to allow release of the birds back to the wild.

Role of gonadal and adrenal steroids and thyroid hormones in the regulation of molting in domestic goose

Plasma levels of testosterone (T), 17-β-estradiol (E2), progesterone (P4), dehydroepiandrosterone (DHEA), corticosterone (B), thyroxine (T4) and triiodothyronine (T3) were monitored during postnuptial and the prenuptial molt in domestic goose (Anser anser domesticus) in both sexes. 1. At the beginning of postnuptial molt (when the old, worn dawny-, and cover feathers' loss starts) in ganders, the levels of T, E2, P4 decrease while DHEA and B significantly increase. The elevated levels of T4 and low T3 concentrations characteristic of the last phase of the reproduction, remain unchanged. In layers, similar changes were observed, however, B decreases. 2. In the early phase of outgrowth of wing and cover feathers, plasma levels of T, E2 and P4 are low. Elevated B, DHEA and T4 concentrations decrease in ganders, while in layers DHEA increases and B and T4 levels remain unchanged. T3 increases in both sexes. 3. The subsequent intensive outgrowth period of wing- and cover feathers both in ganders and in layers is characterized by very low levels of T, E2, DHEA and T4, but P4 increased, and T3 concentration remain high. 4. At the end of postnuptial molt - when the outgrowth of dawny, cover-, and wing feathers stops - very low T, E2, P4, DHEA and T4 levels and and high T3 plasma levels were found in both sexes. Fast increase of plasma B was detected in ganders, while in geese, B concentration remain high. 5. During prenuptial molting (outgrowth of contour and tail feathers) low E2, P4 and T4, increasing T and DHEA, but very high T3 and B plasma concentration were measured in ganders. In layers, very low T, E2, P4, DHEA and T4 levels, and very high B and T3 levels were found. 6. At the beginning of the fall-winter sexual repose (postmolting stage) T, E2, P4, DHEA and T4 levels increase, T3 and B declines in both sexes. 7. In the subsequent phase of fall-winter period (preparatory stage) there is a further increase in T, P4 and T4, a fast increase of B and a decrease of E2, DHEA and T3 in ganders. In layers, T, P4 and DHEA decrease, B increases and the T4 and T3 do not change. 8. At the beginning of reproduction high T level, unchanged DHEA, slightly declined P4, and decreased E2, T4, T3 and a strong decline of B concentrations occur in ganders. In layers, T is further increased, E2 and P4 shows high levels, and, at the same time DHEA and T3 remain unchanged, while B and T4 decrease.

Postprandial biochemistry changes in penguins (Spheniscus demersus) including hyperuricemia

In a clinical setting, it is important to differentiate abnormal values that may be a normal change resulting from feeding and those that may be disease related. Such postprandial changes have been identified in mammalian and avian species. In the current study, pre- and postvalues for several routine biochemical analytes from penguins (Spheniscus demersus) were examined. Significant increases were found in uric acid, triglycerides, and bile acids (P < 0.001). Uric acid levels increased more than threefold. These data indicate that postprandial changes should be considered when interpreting abnormal biochemistry values in penguins.

Dietary thyroxine induces molt in chickens (Gallus gallus domesticus)

Thyroxine increases during a molt in wild and captive birds, and thyroidectomy prevents induction of molt. This trial examined the effect of dietary thyroxine on molt induction molt in chickens (laying hens, 59 weeks of age). In a completely randomized design (n=15 hens/replication; 6 replications/treatment), hens were randomly assigned to either a traditional molting program consisting of feed withdrawal (FWD), or to diets containing 40 mg thyroxine/kg diet (HT), 20 mg thyroxine/kg diet (LT), or 40 mg thyroxine from thyroactive iodinated casein/kg diet (TIC). The molting treatment lasted 7-13 d, until egg production reached 0%. After molt induction, birds had ad libitum access to the same diet, until egg production was re-initiated and maximized ( approximately 56 d). All treatments induced molt, based upon cessation of egg laying and regression of ovary and oviduct. Birds on FWD treatment lost more body weight during the molting period, but gained more after molt compared to thyroxine treatments (P<0.01 for each), although all body weights were similar when egg production was maximized. Data demonstrate that oral thyroxine, in purified or non-purified form, induces a molt and may enhance animal well-being by reducing the need for FWD.