Free-living male brown-headed cowbirds were captured during the breeding season, implanted with testosterone-filled Silastic tubing, and released. Radioimmunoassay verified that the implants maintained circulating plasma testosterone values at maximal breeding season levels well beyond the normal time of decline. Survival to the following year of these implanted males was compared with survival of unimplanted birds captured in other years, and also with survival of males given empty implants. Androgen-implanted male cowbirds exhibited significantly reduced survival to the following year compared with either of the control groups, and also exhibited severe injuries not seen in other years. It is suggested that the increased risks associated with prolonged high testosterone levels act as a selective force to maintain reduced androgen levels except during the period of aggressive intrasexual interactions that characterizes the reproductive season. Further, it is proposed that the nature and importance of the different risks vary with a species' mating system.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/0018-506x(89)90059-7 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Impact of trypanosomiasis on male camel infertility.
Front Vet Sci
January 2025
Zoology and Entomology Department, Faculty of Science, New Valley University, El-Kharga, Egypt.
Introduction: Blood parasitism is a significant clinical disease that silently undermines the livestock industry, particularly affecting camels. This study aimed to assess the prevalence of in Arabian camels () and its impact on infertility by examining serum protein fractions, lipids, reproductive indices, and the expression of heat shock protein (HSP70) during breeding season.
Methods: A total of 107 male post-pubertal camels, aged between 5 and 10 years, were collected randomly from slaughtering house in Assiut Governorate, Egypt.
Changes in lake sturgeon spawning periodicity is associated with prior reproductive effort.
Sci Rep
January 2025
Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, USA.
Long-lived iteroparous organisms vary resource expenditures toward migration and reproduction in response to individual physical factors and conspecific interactions, which can affect future reproductive timing and interval. Reproductive actions can lead to trade-offs associated with allocations to current vs. future reproduction, including longer reproductive interval, require additional study.
View Article and Find Full Text PDFAnalysis and Identification of Polyphenols in Fragaria, Rubus, and Ribes Species by Nontargeted UHPLC-PDA-MS Metabolite Profiling.
Methods Mol Biol
January 2025
Environmental and Biochemical Sciences, James Hutton Institute, Dundee, Scotland, UK.
Profiling of secondary metabolites within Fragaria sp. (strawberry), Rubus sp. (raspberries and blackberries), and Ribes sp.
View Article and Find Full Text PDFThe plainfin midshipman fish (Porichthys notatus) relies on the production and reception of social acoustic signals for reproductive success. During spawning, male midshipman produce long duration advertisement calls to attract females, which use their auditory sense to locate and access calling males. While seasonal changes based on reproductive state in inner-ear auditory sensitivity and frequency encoding in midshipman is well documented, little is known about reproductive-state dependent changes in central auditory sensitivity and auditory neural responsiveness to conspecific advertisement calls.
View Article and Find Full Text PDFCorticosterone predicts double-brooding in female savannah sparrows (Passerculus sandwichensis).
Horm Behav
January 2025
Department of Integrative Biology, University of Guelph, 50 Stone Road, E, Guelph, Ontario N1G 2W1, Canada.
Given that double-brooding (rearing two broods within a season) can increase annual fecundity, it is unclear why some females in multi-brooded populations rear only one brood per season. The Quality Hypothesis proposes that double-brooded females are high quality and, thus, have sufficient energetic resources available to bear the costs of rearing two broods per season. Glucocorticoids - endocrine hormones that have a critical role in energy regulation - could reflect female quality, and, therefore, also have the potential to indicate whether a female will rear a second brood.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!