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My Frog’s Color is Fading! Diet Changes can Brighten Frog Colors

Congo Reed Frog

Uploaded to Wikipedia Commons by Nhobgood

Frogs that are clad in yellow, orange, and red, such as Fire-Bellied Toads and Red-Eyed Treefrogs, often become somewhat dull in coloration after a time in captivity. I’ve noticed this in a variety of species under my care in zoos and at home, yet the phenomenon is rare in the wild or among animals kept outdoors under semi-natural conditions. Color loss can also indicate a health concern (please see below), but often the affected animals are robust and doing well. A photograph showing an astonishing difference in coloration between Red-Eyed Treefrogs maintained on 2 different diets recently caught my eye, and I thought it might be useful to summarize the related research here.

Acquiring Color: Why are Red Frogs Red?

Pigments known as carotenoids are responsible for most of the orange, red and yellow coloration exhibited by frogs. Color is important not just from an aesthetic point of view (or a monetary one, for those who breed “designer frogs”!) but may also affect breeding success and the ability to hide from or deter predators.

Fire bellied toad

Uploaded to Wikipedia Commons by Pkuczynski

In addition to these roles, carotenoids also act as antioxidants and function in the immune and other systems. Carotenoids are manufactured by plants, bacteria and fungi; frogs and other vertebrates must obtain them from their diet.

Improving the Carotenoid Content of Feeder Insects

Researchers at the University of Manchester and the Chester Zoo investigated carotenoid levels in three species of crickets and three different cricket diets (Zooquaria, No. 5, p.6). One of those studied, the Domestic or House Cricket, Acheta domesticus, is used for pet food in the USA. The others – the Tropical House Cricket, Gryllodes sigillatus, and the Mediterranean Field Cricket, Gryllus bimaculatus – are more commonly seen in European and Asian collections.   A diet comprised of fruits and vegetables provided crickets with the highest carotenoid levels. A tropical fish food (flakes) diet resulted in intermediate carotenoid levels, and the lowest levels were seen in crickets feeding upon wheat germ and other grains.   Mediterranean Field Crickets achieved higher concentrations than did the other species, but none retained carotenoids for very long. Carotenoid levels plummeted within 48 hours, so gut-loaded crickets should be used within a day or so after consuming fruits, vegetables and other carotenoid rich foods; please see the article linked below for further information.

Painted Mantella

Uploaded to Wikipedia Commons by Esculapio

Future Research

Although the study was spurred by an interest in the effect of carotenoids on the immune system, the coloration aspect is starting to attract attention (please see photos of red-eyed treefrogs here). Further study is needed, but it’s clear that adding fruits and vegetables to the diets we provide crickets, roaches and other feeders makes good sense. Bear in mind also that this study looked at one aspect of diet…fresh produce no doubt offers a wide variety of other health benefits.   As a novice bird keeper long ago, I learned that flamingos denied sufficient shrimp and canthaxanthin soon “bleach-out”…today we still know far more about this topic as it relates to birds than to amphibians. But some of that knowledge may have applicability to herps – in any event, I hope that more private keepers and researchers will take an interest. I’ll stay alert for updates; in the meantime, please post any relevant thoughts and links below, thanks. Hi, my name is Frank Indiviglio. I’m a herpetologist, zoologist, and book author, recently retired from a career spent at several zoos, aquariums, and museums, including over 20 years with the Bronx Zoo. Please check out my posts on Twitter and Facebook.   Each day, I highlight breaking research, conservation news and interesting stories concerning just about every type of animal imaginable. I look forward to hearing about your interests and experiences as well, and will use them in articles when possible.   Please also post your questions and comments below…I’ll be sure to respond quickly. Thanks, until next time, Frank.  

Further Reading

Nutritious Foods for Frogs and Toads Cricket Nutrient Level Study Cricket Care and Feeding

2 comments

  1. avatar

    http://www.dendroboard.com/forum/food-feeding/135906-new-scientific-publication-pdfs-carotenoids.html

    This may be of interest.

    It appears carotenoids are pretty complex group of compounds and different ones have different benefits in the animal diet. In particular a lot of focus on astaxanthin. After reading this I began adding Repashy Superpig to my FF media as well as dusting with Paracoccus powder and Spirulina. My pair of pumilio are raising tadpoles so at least it doesn’t hurt…and may even help as the study shows.

    All the Best
    ~Joseph See

  2. avatar

    Thanks, Joseph, nice to hear from you. I hope all is well.

    Please keep me posted, enjoy, Frank

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About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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