Graham S.P.,31 Funchess Hall |
Soehren E.C.,Natural Heritage Section |
Cline G.R.,Jacksonville State University |
Schmidt C.M.,31 Funchess Hall |
And 4 more authors.
Herpetological Conservation and Biology | Year: 2011
Hellbenders (Cryptobranchus alleganiensis) historically occurred in large numbers in the eastern United States, but they have undergone a considerable decline due to habitat modification and its subsequent effects on stream quality. To evaluate the Hellbender's current status in Alabama, we verified several recent anecdotal sightings of Hellbenders, and conducted 355 person hours of surveys and 31 trap nights in most historical collection localities and at several additional sites that we considered suitable for this species. We failed to find any Hellbenders during our survey. If Hellbenders still exist in Alabama, they represent relict populations that occur in very low population densities, and likely will be extirpated from the state in the near future. The apparent decline and possible extirpation of Hellbenders in Alabama is probably related to degradation of habitat and water quality resulting from large scale impoundments and land use patterns. As such, land use and water utilization practices will likely persist, and we recommend that conservation efforts intended for this species in Alabama be focused on other species, or on other areas of this species' range where conservation success is more feasible. © 2011. Stephen De Lisle. All Rights Reserved.
Hawkins G.L.,Elias |
Hill G.E.,31 Funchess Hall |
Mercadante A.,31 Funchess Hall
Biological Reviews | Year: 2012
Delayed plumage maturation is the delayed acquisition of a definitive colour and pattern of plumage until after the first potential breeding period in birds. Here we provide a comprehensive overview of the numerous studies of delayed plumage maturation and a revised theoretical framework for understanding the function of delayed plumage maturation in all birds. We first distinguish between hypotheses that delayed plumage maturation is attributable to a moult constraint with no adaptive function and hypotheses that propose that delayed plumage maturation is a component of an adaptive life-history strategy associated with delayed reproductive investment. We then recognize three potential benefits of delayed plumage maturation: crypsis, mimicry and status signaling. Evidence suggests that delayed plumage maturation is not a consequence of developmental constraints and instead represents a strategy to maximize reproductive success in circumstances where young adults cannot effectively compete with older adults for limited resources, particularly breeding opportunities. A multi-factorial explanation that takes into account lifespan and the degree of competition for limited breeding resources and that combines the benefits of an inconspicuous appearance with the benefits of honest signaling of reduced competitiveness provides a general explanation for the function of delayed plumage maturation in most bird species. Delayed plumage maturation should be viewed as a component of alternative reproductive strategies that can include delay in both plumage and sexual development. Such strategies are frequently facultative, with individuals breeding prior to the acquisition of definitive plumages when conditions are favourable. Presumably, the benefits of delayed plumage maturation ultimately enhance lifetime reproductive success, and studying delayed plumage maturation within the context of lifetime reproductive success should be a goal of future studies. © 2011 The Authors. Biological Reviews © 2011 Cambridge Philosophical Society.