Amphibians have cutaneous glands on their skin which produce a number of toxic compounds that serve as protection against predators and microorganisms. Cane toads (Rhinella marina) have large parotoid glands located on their shoulders to store toxins, many of which are derived from lipids and are thus energetically expensive to produce. I used a combination of field and laboratory studies to investigate behavioral and physiological consequences of toxin loss and replenishment in cane toads. In a cross-sectional study, free-ranging toads were euthanized and dissected to identify correlations between toxin content and morphology /physiology. Experimental manipulations (manually expressing toxin from glands) were performed to mimic a predator encounter that resulted in toads expelling their toxin in defense. A control group for this manipulation consisted of individuals whose glands were squeezed in a manner that did not express the toxin. Manipulations were carried out in both captivity and in the field. In both settings, growth rate, behavior, activity and energy allocation (relative organs masses) were compared between de-toxined and control toads. A significant negative correlation between toxin content and liver mass was evident among wild toads. The experimental manipulation of removing toxin affected change in body mass in both captive and radio-tracked wild toads. However, the effect on mass changed differed between captive and wild settings. De-toxined toads that were fasted exhibited poorer locomotor performance than their control counterparts. However, toxin milking had no significant effect on personality traits, such as boldness, or foraging skills. Radio-tracking demonstrated that de-toxined toads also disperse more slowly than the control toads, preferring to stay closer to the water source at which they were originally captured. I found evidence of physiological and behavioral costs associated with toxin removal, Blennerhassett 3 even over a relatively short period (5-20 days). Therefore, toxin may represent a precious commodity to its host and may only be deployed as a last line of defense.
Key words: Bufo marinus, parotoid glands, radio-telemetry, toxin production, toxin replenishment.
Biodiversity | Biology | Ecology and Evolutionary Biology | Toxicology
Blennerhassett, Ryann, "The value of chemical defense: the effects of toxin milking on the physical, physiological, and behavioral performance of cane toads (Rhinella marina)" (2018). Independent Study Project (ISP) Collection. 2952.