نتایج جستجو برای: seasonal reproductive

تعداد نتایج: 158986  

Journal: :American journal of primatology 2015
Marina B Blanco Emilienne Rasoazanabary Laurie R Godfrey

Small-bodied, nocturnal mouse lemurs (Microcebus) are widespread across diverse forest habitats in Madagascar. They are strict seasonal breeders and can, depending on the habitat and species, undergo daily or prolonged torpor to minimize energy expenditure during periods of food and water scarcity. Duration of reproduction, number of litters per season and timing of births vary across individua...

2016
Gregory T. Wann Cameron L. Aldridge Clait E. Braun

Animal populations occurring at high elevations are often assumed to be in peril of extinctions or local extirpations due to elevational-dispersal limitations and thermoregulatory constraints as habitats change and warm. However, long-term monitoring of high-elevation populations is uncommon relative to those occurring at lower elevations, and evidence supporting this assumption is limited. We ...

2016
Hai-Jun Xiao Xiao-Wei Fu Yong-Qiang Liu Kong-Ming Wu

Annual migration of pests between different seasonal habitats can lead to serious crop damage. Reproductive immaturity is generally associated with the migratory process (oogenesis-flight syndrome), but the mechanism of reproductive development during migration varies unpredictably. Here, the vitellogenin gene (MsVg) and three key regulatory enzyme genes (MsJhamt, MsJheh and MsJhe) related to j...

Journal: :Proceedings. Biological sciences 2010
Kathleen G O'Malley Michael J Ford Jeffrey J Hard

Seasonal timing of life-history events is often under strong natural selection. The Clock gene is a central component of an endogenous circadian clock that senses changes in photoperiod (day length) and mediates seasonal behaviours. Among Pacific salmonids (Oncorhynchus spp.), seasonal timing of migration and breeding is influenced by photoperiod. To expand a study of 42 North American Chinook ...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 1999
G E Bentley T J Van't Hof G F Ball

Neuroplasticity in the vocal control system of songbirds is strongly influenced by seasonal fluctuations in circulating testosterone. These seasonally plastic telencephalic structures are implicated in the learning and production of song in songbirds. The role of the indoleamine melatonin in seasonal adaptations in birds has remained unclear. In this experiment, European starlings were castrate...

Journal: :Ecology 2017
Joseph A LaManna Thomas E Martin

Increased perceived predation risk can cause behavioral and physiological responses to reduce direct predation mortality, but these responses can also cause demographic costs through reduced reproductive output. Such indirect costs of predation risk have received increased attention in recent years, but the relative importance of direct vs. indirect predation costs to population growth (λ) acro...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 1985
D J Earnest F W Turek

A pharmacological approach was used to examine the role of acetylcholine in the photic control of circadian rhythms and seasonal reproductive cycles. The experimental protocol was designed to determine whether the administration of carbachol, a cholinergic agonist, could mimic the effects of brief light pulses on gonadal function and/or the circadian rhythm of wheel-running activity in golden h...

Journal: :Biology letters 2012
Jamie M Cornelius Creagh W Breuner Thomas P Hahn

Seasonal changes in stress steroid hormone secretions are thought to reflect investment in self-maintenance versus reproduction. The capricious conditions hypothesis (CCH) posits that reduced corticosterone (CORT) secretion during stress coincident with parental phases of breeding is necessary in harsh environments because a full response would otherwise trigger repeated nest abandonments. To t...

Journal: :The Proceedings of the Nutrition Society 1994
A S Loudon

For wild animals, food availability usually exhibits considerable seasonal fluctuations and as a result dramatic seasonal variations in body weight, fatness and food intake are often observed. Birds and mammals living in the temperate zones or higher latitudes, therefore, time the onset of reproductive activity each year with great precision so that young are produced at the most propitious tim...

2014
Yolanda E Morbey Evelyn L Jensen Michael A Russello

Seasonal declines of fitness-related traits are often attributed to environmental effects or individual-level decisions about reproductive timing and effort, but genetic variation may also play a role. In populations of Pacific salmon (Oncorhynchus spp.), seasonal declines in reproductive life span have been attributed to adaptation-by-time, in which divergent selection for different traits occ...

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