FIELD USE OF MAXIMAL SPRINT SPEED BY COLLARED LIZARDS (CROTAPHYTUS COLLARIS): COMPENSATION AND SEXUAL SELECTION

Evolution ◽  
2006 ◽  
Vol 60 (9) ◽  
pp. 1888 ◽  
Author(s):  
Jerry F. Husak ◽  
Stanley F. Fox
Keyword(s):  
Sexual Selection ◽  
Crotaphytus Collaris ◽  
Sprint Speed ◽  
Collared Lizards

scholarly journals Integrating bioenergetics and conservation biology: thermal sensitivity of digestive performance in Eastern Collared Lizards (Crotaphytus collaris) may affect population persistence

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Casey L Brewster ◽  
Jason Ortega ◽  
Steven J Beaupre
Keyword(s):  
Thermal Sensitivity ◽  
Metabolizable Energy ◽  
Effect Of Temperature ◽  
Valuable Insight ◽  
Feeding Rates ◽  
Crotaphytus Collaris ◽  
Reduced Body ◽  
Heat Loads ◽  
Passage Times ◽  
Collared Lizards

Abstract Information on bioenergetics can provide valuable insight into the ecology, life history and population dynamics of organisms. For ectothermic animals, thermal sensitivity of digestion is an important determinant of net assimilated energy budgets. A recent study in the Ozark Mountains indicated that eastern collared lizards (Crotaphytus collaris) restricted to encroached glades (characterized by woody vegetation encroachment) experience reduced environmental heat loads and have reduced age-specific growth and reproductive rates compared to populations in intact glades. To assess the potential impact of reduced body temperatures on assimilation rates of C. collaris in encroached glades, we conducted feeding trials across four temperature treatments (28, 31, 34 and 37°C). We tested for temperature effects on voluntary feeding rates, passage times, apparent assimilated energy (AE) and metabolizable energy (ME). Passage times decreased and voluntary feeding rates increased significantly with increasing temperature. Consumption explained the majority of variance in AE and ME, followed by the effect of temperature treatments. Using data on voluntary feeding rates, passage times and ME as a function of temperature, we estimated over a 10-fold increase in predicted daily assimilated energy across temperature treatments (28°C = 0.58 kJ/day, 31°C = 1.20 kJ/day, 34°C = 4.30 kJ/day, 37°C = 7.95 kJ/day). Thus, lower heat loads in encroached glades may cause reduced body temperature and result in restricted energy assimilation rates. Our study provides a novel approach to the integration of bioenergetics and conservation and shows the efficacy of using information on digestive performance to investigate underlying mechanisms in a conservation context.

Juvenile-juvenile social signalling: a case for precocial sexual selection in the collared lizard, Crotaphytus collaris (Squamata: Crotaphytidae)?

2020 ◽  
Vol 130 (2) ◽  
pp. 336-344
Author(s):  
Stanley F Fox ◽  
Felipe De Jesús Rodríguez-Romero ◽  
Andrea Acevedo Crosby
Keyword(s):  
Sexual Selection ◽  
Social Interactions ◽  
Social Relations ◽  
Sexual Maturity ◽  
Field Experiments ◽  
Crotaphytus Collaris ◽  
The Social ◽  
Collared Lizard ◽  
Juvenile Males ◽  
Sexually Mature

Abstract Sexual selection is widespread in animals, but quite naturally studied in adults. Juvenile males in most animals are not differentiated from females and coloration is usually drab. However, there is no reason to suspect that sexual differences cannot develop before puberty, influence social interactions, and then have fitness pay-offs later in life. Juvenile collared lizards (Crotaphytus collaris (Say, 1822)) show marked dichromatism: males develop bright dorsolateral orange bars whereas females do not. These juvenile orange bars (JOB) disappear at sexual maturity, when males develop different colour traits maintained by sexual selection. We conducted field experiments with juvenile males on their developing territories in which we utilized staged intruders of juvenile males (with JOB) and juvenile females (lacking JOB) and also juvenile male intruders whose JOB were manipulated. Residents reacted significantly more aggressively toward males vs. females, and also toward males whose JOB were emphasized with paint than those whose JOB were masked by paint. These JOB are used in signalling among juveniles and we suggest the social relations established then are retained until sexual maturation the next spring (after the JOB are lost) to benefit males that previously displayed strong JOB by increased matings in the spring as sexually mature yearlings as per a phenomenon we call precocial sexual selection.

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