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A Monitor First – Male Rosenberg’s Monitors Cover and Guard Nests

Water MonitorI remain awed by the learning abilities and complex behaviors evidenced by the Water and Lace Monitors I cared for at various zoos…spend time with any species and you’ll quickly see why.  Despite being popular study subjects, monitors are constantly surprising us.  For example, the current issue of The Journal of Herpetology (V44, N3, Sept 2010) documents an entirely new behavior for any monitor species – cooperative nest building and nest guarding in Rosenberg’s Monitor (Varanus rosenbergi).

Nest Defense by both Sexes

A 16-year-long study of this species on Australia’s Kangaroo Island has revealed that females guard their nest sites for up to 3 weeks after egg deposition, a behavior that has not been documented for any other monitor (3 species, including the Komodo Dragon, may return to the nest site on occasion, but seem not to remain nearby).  Amazingly, in 8 instances a male joined the female in protecting the eggs.

Other Rosenberg’s Monitors are the primary threat to eggs.  Females guarding nests attacked male intruders twice their own weight, and repelled them in most cases.  The vicious fights that ensued frequently left both combatants with deep wounds and broken ribs and limbs.  In those cases where males were also on guard duty, they too joined in the frays, but females were clearly the more aggressive of the pairs.

Cooperative Nest Construction

Termite Mound AustraliaFemale Rosenberg’s Monitors exclusively chose termite mounds as nest sites.  In occupied mounds, the resident termites usually closed the nest entrance hole within 3-5 hours after egg deposition.  If they did not, the female monitor finished the job.

In another unexpected turn of events, male monitors assisted females in covering nests on 5 occasions.


Further Reading

Learning in Monitors and Other Lizards

Australian Government Report, Rosenberg’s Monitor – natural history, conservation plan, photos.

Water Monitor image referenced from wikipedia and originally posted by Rob and Stephanie Levy
Termite Mound in Australia image referenced from wikipedia and originally posted by Alchemist-hp

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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