That caught your attention, didn’t it?

I bought a book off Amazon years ago, not knowing entirely what it was about. It could have been partially attributed to the discovery of buying stuff over the Internet, but the title did beckon at me from my computer screen.

This is the book in question; “Biological Exuberance: Animal Homosexuality and Natural Diversity” by author Bruce Bagemihl. It touches on the topic of animal behaviour that continues to debated by many scientists. And while there is plenty of evidence, it is difficult to extrapolate this evidence because of the human tendency to anthropomorphise such behaviour. Author Bruce Bagemihl himself highlights it in his book in the introductory passages.

So what about animal homosexuality? There is no reproductive benefits for two conspecific males to be engaging in reproductive behaviour with each other, with the exception of Sea Hares (Aplysia species and related genera) that are mostly hermaphrodites. What is the purpose of animal homosexuality?

Most observed cases of animal homosexuality occurs in animal groups with some form of social structure. For example, when male lions (Panthera leo) come of age, they are chased away from the pride they grew up in and begin a nomadic lifestyles until they find their own pride. Male lions have been reported to form pair-bonds with other solitary male lions, displaying affectionate activity with each other like mutual grooming, rubbing of heads and, in some cases, sexual activity between two males occurs. The same thing can be said about female lions as well.

There is no reproductive benefit among homosexual pair-bonds, but eventually, when a nomadic male lion finally becomes a resident in a pride, they have extraordinarily high heterosexual copulations with females, and vice versa.

In 2004, two male chinstrap penguins (Pygoscelis antarcticus) at New York’s Central Park Zoo made news when they were observed to have exhibited pair-bonding behaviour with each other already for six years running. Wild birds have also been observed such activity, the most notable being swans. Black swans (Cygnus atratus) and mute swans (Cygnus olor) have know to form homosexual pair-bonds and still exercise nest-building and (in females) egg-laying behaviour (even though the eggs are infertile).

So what is the benefit of homosexuality in animals? It has been noted that homosexual pair-bonds occur most frequently in animals that are rely heavily on social interaction or in unnatural environments (for example, zoos). There may be some benefit for animals that pair-bond. Taking male nomadic lions that pair-bond as an example, nomadic lions that stick together often have a higher chance of survival compared to a nomadic lion roaming by itself. Some birds that pair-bond share duties, such as foraging for food or protecting the nest, behaviour that may normally often identified in normal heterosexual pair-bonds.

Ultimately, animal homosexuality should not be viewed as an abnormality but as an aspect of biodiversity that is just waiting to be uncovered. There are still many questions to be asked and new aspects of the diversity of the animal kingdom (and ultimately, ourselves) still left to be discovered. Until then, all we can do is to marvel at why some animals do the things they do.


  • Bagemihl, Bruce. Biological Exuberance. Stonewall Inn Editions, 2000. Print.
  • Meyer-Bahlburg, Heino F. L. “Sex hormones and male homosexuality in comparative perspective.” Archives of Sexual Behavior 6.4 (1977): 297-325. Web. 8 Apr 2010. <http://www.springerlink.com.libproxy1.nus.edu.sg/content/g4757213w9045228/>.
  • “Aplysiomorpha.” 2010. Web. <http://en.wikipedia.org/wiki/Aplysiomorpha>.
  • “Homosexual behavior in animals.” 2010. Web. <http://en.wikipedia.org/wiki/Homosexual_behavior_in_animals>.
  • Owen, James. “Homosexual Activity Among Animals Stirs Debate.” National Geographic News 23 July 2004: n. pag. Web. 8 Apr 2010. <http://news.nationalgeographic.com/news/2004/07/0722_040722_gayanimal.html>.
  • “Book Cover Page.” Web. 9 Apr 2010. <http://jacketupload.macmillanusa.com/jackets/high_res/jpgs/9780312253776.jpg>.
  • “Two Giraffes.” Web. 9 Apr 2010. <http://en.wikipedia.org/wiki/File:Two_Giraffes.PNG>.
  • “Black swans.” Web. 9 Apr 2010. <http://en.wikipedia.org/wiki/File:Black_Swans.jpg>.
  • “Two male mallards.” Web. 9 Apr 2010. <http://en.wikipedia.org/wiki/File:Males_Anas_platyrhynchos_2_.jpg>.

Laying eggs in other insect’s larvae

The  Ichneumon Wasps that belong to the family Ichneumonidae have 2 very unique behaviors and there are almost 60,000 different species of lchneumon Wasps worldwide. One very significant difference between the ichneumon wasps and the normal wasps is that the former have an antennae of more than 16 segment while the latter only have 13 or less. The female ichneumon wasps also have an ovipositor that is longer than its’ body. They have a very unique way of using the ovipositor. This will be shown in the video which featured the Anomaloninae species of the ichneumon wasps. 

A species of ichneumon wasp

A species of ichneumon wasp

As highlighted in the video, the 1st part of the video shows that the wasps are able to find nests that contain host larvae and after entering the nest, it will release a special pheromones to cause confusion among the attackers causing them to attack one another instead of the ichneumon wasp.

Another species of ichneumon wasp

Another species of ichneumon wasp

Next i will talk about an unique reproduction behavior of the ichneumon wasp. Different species of ichneumon wasps will lay their eggs in the larvae of different insects. These insects include beetles and butterflies. In the video, we are able to see that once the ants started attacking one another, the wasp will approach the larvae of the butterfly that is also in the ant nest. It will then lay its eggs into each of the butterfly larvae and then it will leave the ant nest. Surprisingly, the ichneumon wasps are able to sense/find the ant nest with the butterfly larvae correctly. More info of this behavior can also be found in the science journal found at:  http://www.springerlink.com/content/u5lk77h230328066/

The link to the video is as follows: Ichneumon wasp on youtube


“The ichneumon wasp”  Youtube. URL: http://www.youtube.com/watch?v=SLvuevf__Ok (Accessed on 6th April 2010)

“Ichneumonidae” URL: http://en.wikipedia.org/wiki/Ichneumonidae (Accessed on 6th April 2010)

“Entomologia Experimentalis et Applicata, 15 (2): 190-194, June 1972.  The ichneumon wasp venturia canescens: oviposition and avoidance of superparasitism (David Rogers)

“It is alright that we are blind, because we have internal compass!”

The Blind Mole Rat

Blind mole rats (Spalax ehrenbergi), as the name suggested, they are totally blinded. Not only does this animal lack of eyesight, they dig and inhabit in their own tunnel system which has no above ground exits. What so special about these creatures is that they possess a rare talent, that is they are able to use the Earth’s magnetic field on long journeys, much like a compass, to continuously monitor and maintain its course.

To forage for food, these creatures have to dig over a great distance; hence they are not able to afford to make navigational mistakes. While, sighted animals like us are able to make use of the visual landmarks to alter our directions, the blind mole rats make use of magnetic field to change their navigational strategy accordingly.
In the experiments done by Talikimchi and Joseph Terkel, results shown that these creatures were less likely to lost their way under the altered magnetic field when they had to travel short distances. This result indicates that the blind mole rats will switch to using the Earth’s magnetic field as a reference point when navigating over long distances.
Another interesting research found by Talikimchi and Joseph Terkel published in the November 2003 issue of the science journal Animal Behaviour, shows that blind mole rats have another special ability that is that they are able to detect dangers before they encounter it. During the study, the creature’s tunnels were being blocked. However, they were able to dig another shortest route around the obstacles to reconnect them. Amazingly, these creatures left a safe margin of 10 to 20 cm. when an obstacle was placed asymmetrically across the tunnel, the mole rats always detoured it on the shorter side. The scientists believe that these creatures are able to detect dangers by using seismic waves that was generated by banging their heads against the earth.
I was really amazed by the blind mole rats’ ability to direct their way using magnetic field, and most importantly, they are able to predict dangers ahead and thus avoid them.


1) Magnetic Compass Orientation in the blind mole rat (Spalax Ehrenbergi). By Talikimchi and Joseph Terkel. Department of Zoology, George S. Wise Faculty of Life Sciences. Accepted 21 November 2000; published on 1 February 2001. URL: http://www.britannica.com/bps/additionalcontent/18/12261107/How-blind-mole-rats-find-their-way-home

2) Subterranean Rodents: News from Underground. By Sabine Begall, Hynek Burda and Cristian E. Schleich . Publisher Springer Berlin Heidelberg. ISBN 978-3-540-69275-1 (Print) 978-3-540-69276-8 (Online). Page 3-9. (Accessed: 6 Apr 2010)

3) “Rat Radar: Rodent Uses Natural “GPS”” by John Pickrell in England. National Geographic News. January 29, 2004. URL: http://news.nationalgeographic.com/news/2004/01/0129_040129_blindmolerat.html (Accessed: 6 Apr 2010)

4) “Internal Compass Helps Blind Mole Rat Find Its Way” by Sarah Graham January 20, 2004. URL: http://www.scientificamerican.com/article.cfm?id=internal-compass-helps-bl ( Accessed: 6 Apr 2010)