Parental Infanticide: Children for Breakfast?

Eclectus parrots, Eclectus roratus, exhibit reverse sexual dichromatism which means that males and females differ in terms of colouration (see fig.1). In eclectus parrots, stark differences in colour of the beak and plumage are evident from as early as when they are nestlings. In fact it is interesting to note that till a few decades ago scientists believed that the two were different species altogether!

Male (left) and female (right) eclectus parrots perched on branch.

Fig 1: Male (left) and female (right) eclectus parrots perched on branch.

However, this reverse sexual dichromatism is not merely of aesthetic significance. The eclectus parrot is reknowned for being able to exercise extreme bias in sexual allocation. Hence, this is the reason why: “one eclectus in Chester Zoo produced 30 sons before the first daughter was produced” (Heinsohn et al., p. 1325). So what is the secret behind being able to maintain such a remarkable bias in sexual allocation?

Fig. 2: on day 3 this check is already clearly a male due to its yellow beak.

Heinsohn recognises the likelihood, yet until further study merely specualtion, of bias to occur at fertilization and probably, during ovulation (ibid., p. 1328). However, scientists also recognise that infanticide and cannibalism is likely because nestlings go missing and no remains are found. In addition, since eclectus parrots can be easily sexed after hatching, the parents job of sexing their children is made appraent at first sight. Therefore, eclectus parrots it is either ‘death or love at first sight’. Siblicide is common amongst birds when the youngest nestlings are pushed off the nest. However, parental infanticide is a less well known area of study which Heinsohn promises to look at in closer in detail in his studies to come.

Closer to home, more substantial evidence of parental infanticide and cannibalism can be found in the case of the Oriental Pied Hornbill, Anthracoceros albirostris, in Singapore (photgrpahic evidence is included). Afterall, one may have to conlcude that parental supervision may not always be the best thing for children!!!


R. Heinsohn, S. Legge & S. Barry, 1997. Extreme bias in sex allocation in Eclectus parrots. Proceedings of the Royal Society, Biological Sciences, 264: 1325-1329.

Ellegren H, Gustaffson L & Sheldon BC, 1996. Sex ratio adjustment in relation to paternal attractiveness in a wild bird population. Proceedings of National Academy of Science USA, 93(21):11723-11728.

Kevin J McGraw & Mary C Nogare, 2005. Distribution of unique red feather pigments in parrots. Biology Letters, 1, 38-43.

“Infanticide-cannibalismm in Oriental Pied Hornbill,” Prof Ng Soon Chye et al. Bird Ecology Study Group, 09 Apr. 2009. URL: http://besgroup.talfrynature,com/2009/04/09/infanticide-cannibalism-in- oriental-pied-hornbill/ (accessed: 9 Apr. 2010).

“Oriental Pied Hornbill: Parental infanticide,” Marc Cremades & Prof Ng Soon Chye. Bird Ecology Study Group, 07 Jun. 2007. URL: (accessed: 9 Apr. 2010).

Baloo, the baby killer?

sloth bear with cub

Baloo, the Baby Killer?

I recently chanced upon an article from the Asian Geographic magazine which suggested the possibility of the adult male of the sloth bear, Melursus ursinus, to be a threat to the cubs of its own species. (Baloo from the Jungle Book, 2010) Now this is surprising revelation, as anyone who has seen the classic Disney film animation, The Jungle Book, would know that Baloo, the sloth bear in the movie, is portrayed as the alternative “mentor” to Mowgli, the man-cub, teaching him how to lead a carefree “slacker” lifestyle by living off the jungle. (The Jungle Book [1967 film]) The incongruity of Disney choosing an animal that could possibly have infanticidal tendencies as Mowgli’s mentor was apparent to me. I was intrigued to find out why animals, in particular the sloth bear, would kill their offspring.

Research shows that infanticide is common in the animal kingdom, and there are varying explanations for its occurrence. One main explanation is that the individuals responsible for infanticide benefit by gaining fitness through several sources that include: “(1) exploitation of the infant as a resource, (2) elimination of a competitor for resources, (3) increased maternal survival or lifetime reproductive success for either mother or father by elimination of an ill-timed, handicapped, or supernumerary infant, and, finally, (4) increased access for individuals of one sex for reproductive investment by the other sex at the expense of same-sex competitors.” The last source of benefit mentioned is used to explain sexually-selected infanticide (SSI), which is a common practice with bears. (Hrdy, 1979) There is little research available on SSI occurring amongst sloth bears, although it is well documented amongst other species such as brown bears (Ursus arctos) and polar bears (Ursus maritimus). (Stirling and Derocher, 1990)

In the magazine article, the female sloth bear tending to her cubs that the writer observed became very nervous upon the appearance of a male (which is typically 50 percent heavier than a female). She proceeded by rushing towards the male accompanied by “impressive roars”, a typical mock-charge to deter potential aggression. Considering that the female would probably be severely injured in a confrontation with the male, her counterstrategy to SSI might not be the best. Females of other bear species have been observed to counter male SSI behaviour by becoming sexually promiscuous, effectively mating with every male they chance upon, which would allow the males to mate with the females in the hope that the cubs would be spared. (Bellemain, Swenson and Taberlet, 2006)


“Baloo from the Jungle Book” by Axel Gomille. Asian Geographic , Vol. 72, 3/2010, pp. 32-35.

“The Jungle Book (1967 film)” in Wikipedia. URL: (Accessed on: 09 Mar 2010)

Hrdy, Sarah Blaffer, 1979. Infanticide among animals: A review, classification, and examination of the implications for the reproductive strategies of females. Ethology and Sociobiology, Vol. 1, Issue 1 (October 1979), pp. 13-40.

Ian Stirling and Andrew E. Derocher, 1990. Factors Affecting the Evolution and Behavioral Ecology of the Modern Bears. Bears: Their Biology and Management, Vol. 8 (1990), pp. 189-204.

Eva Bellemain, Jon E. Swenson and Pierre Taberlet, 2006. Mating Strategies in Relation to Sexually Selected Infanticide in a Non-Social Carnivore: the Brown Bear. Ethology,  Vol . 112, No. 3 (2006), pp. 238-246.

Sexually Antagonistic Co-evolution

One of the most fascinating advances in evolutionary biology is in sexually antagonistic co-evolution (SAC). Some male animals have been observed to evolve persistence traits that increase their fitness to mate more successfully vis-à-vis male-male competition for potential mates. In response, their female counterparts have developed resistance mechanisms to reduce the direct costs of increased mating rates, by making it more difficult for males to mate successfully. SAC postulates that subsequently, these male animals evolve even more persistent traits, while females develop greater resistance characteristics, leading to an ever-escalating co-evolutionary “arms race” (Parker, 1979; West-Eberhard, 1983).


One example of SAC has been observed in seed beetles (Coleoptera bruchidae). Spines developed on the male genitalia helps enhance stability when mating and thereby greater success in copulation (Edvarsson & Tregenza, 2005). According to a study published in an online journal by Arnqvist et. al (2007), male seed beetles were recorded to evolve genital spines while female seed beetles developed tougher copulatory ducts to resist the spines. SAC was subsequently observed where male seed beetles developed more spines in response, while their female counterparts developed even stronger copulatory ducts by further reinforcing with thicker tissue. This evolution could be seen in the main pictures below, when comparing related species demonstrating the evolution of related male genital spines from C to B to A.

“Comparison between genital spines in C. analis (A), C. rhodesianus (B) and C. phaseoli (C).”  By Arnqvist et. al (2007) in “Coevolution between Harmful Male Genitalia and Female Resistance in Seed Beetles.”


“Comparison between genital spines in C. analis (A), C. rhodesianus (B) and C. phaseoli (C).”  By Arnqvist et. al (2007) in “Coevolution between Harmful Male Genitalia and Female Resistance in Seed Beetles.” Proceedings of the National Academy of Sciences of the United States of America, Vol. 104, No. 26 (Jun. 26, 2007), pp. 10921-10925. (accessed on 04/04/2010).


Recent research has made SAC more rigorous. Some traits that were thought as primary sexual antagonisms, where the enhancement of such a trait would improve male copulation success, has been shown to be a result of other factors (Svensson & Gosden, 2007). For example, the increased forehead patch size in the collared flycatcher, Ficedula albicollis, has been primarily shown to be a result of climate change, with heightened sexual success a secondary result (Garant et al, 2004; Hegyi et al, 2006). This highlights the different primary causes of evolutionary changes that may have sexually enhancing and subsequently antagonistic consequences, making the study more careful and holistic.




Edvardsson M, Tregenza T (2005) Behav Ecol 16:788-793.

Garant, D., Sheldon, B.C. & Gustafsson, L., 2004. Climatic and temporal effects on the expression of secondary sexual characters: genetic and environmental components. Evolution Vol. 58, 634–644.

Hegyi, G., Torok, J., Toth, L., Garamszegi, L.Z. & Rosivall, B., 2006. Rapid temporal change in the expression and agerelated information content of a sexually selected trait. Journal of Evolutionary Biology Vol. 19, 228–238.

J. Rönn, M. Katvala, G. Arnqvist, 2007. Coevolution between Harmful Male Genitalia and Female Resistance in Seed Beetles. Proceedings of the National Academy of Sciences of the United States of America, Vol. 104, No. 26 (Jun. 26, 2007), pp. 10921-10925

E. I. Svensson & T. P. Gosden, 2007. Contemporary evolution of secondary sexual traits in the wild. Functional Ecology, Vol. 21, 422–433 

West-Eberhard, M.J. ,1983. Sexual selection, social competition and speciation. Quarterly Review of Biology, Vol. 58, 155–183.

Parker, G. A. 1979. Sexual selection and sexual conflict. Pp. 123–166 in M. S. Blum and N. A. Blum, eds. Sexual selection and reproductive competition in insects. Academic Press, New York.

Killer Killer Whales?

On February 24 2010 at SeaWorld Orlando, Tilikum, a 30 year old, 12,000-pound bull killer whale (Orcinus orca), commonly referred to as an orca, grabbed its trainer, Dawn Brancheau, and pulled her underwater, killing her. Her death was the latest in a string of fatalities involving experienced animal trainers and wildlife ‘experts’ (SeaWorld Killer Whale Attacks Trainer: Latest in String of Deaths, 2010), and the third such incident involving this particular ‘whale’ – Orcinus orca is actually the largest member of the dolphin family (Whale Trainer’s Family Speak of Shock at SeaWorld Death, 2010). CBS News Coverage

While orcas may have a fearsome reputation as lethal hunter-killers, there have been very few confirmed human attacks in the wild, and no deaths at all (Orca Shares the Waves with Local Surfer, 2008; Boy Survives Bump From Killer Whale, 2005). However, in captivity, this track record is much more dismal, prompting animal rights activists, such as PETA (People for the Ethical Treatment of Animals), to condemn the confinement of wild, ocean-going mammals to an area, that to them, is “the size of a bathtub” (Whale Trainer’s Family Speak of Shock at SeaWorld Death, 2010). This disturbing divergence in behaviour between wild and captive orcas begs two questions: i) why does captivity make orcas substantially more aggressive, or is it just “Tilly”, as it was nicknamed and ii) what should they do now?

Orcinus Orca

First, Tilly, was a wild orca captured near Iceland in 1983. In the wild, orcas can travel up to 160km per day and occur in all the oceans and most seas. Thus, removing an animal of that size (Tilly is the largest captive orca in the world) from its natural habitat and putting it into a tank causes tremendous stresses from boredom and a lack of exercise for an animal as intelligent, curious and large as orcas (Whale Attack Renews Captive Animal Debate, 2010; Haq, 2010). Orcas also have highly developed and complex social structures (Heimlich & Boran, 2001, p. 35) and the stresses from relative isolation and extrication from its pod may have added to the stress it was feeling. Its reaction could hence have been a way for it to release stress. Earlier in the day, it had refused to cooperate during the killer whale show which may suggest that it was feeling particularly stressed that day.

Second, Tilly is a ‘stud,’ he has sired at least 17 calves since 1992. His high breeding rate and hormone levels may have contributed to its aggressive behaviour. As mentioned previously, Tilly appears to also have a particularly aggressive track record, being linked to the death of another trainer in 1991 and a man who had snuck into his pool in 1999. One of Tilly’s offspring, Ky, has also been linked to an attempted drowning of a trainer at SeaWorld San Antonio, Texas (Haq, 2010). This could very well allude to the fact that Tilly is, as an individually, genetically more predisposed to aggressive behaviour than the average orca. This would make Tilly’s behaviour highly unpredictable and in a sense, ‘expected’ and perhaps should not have even been a part of the show.

Third, an ex-trainer at SeaWorld, Thad Lacinak, has suggested that Tilly might have thought Brancheau’s ponytail floating in the water was a toy and “sucked it in” as part of a game, saying also that certain handling protocol was broken (Ex SeaWorld Official: Trainer Made Mistake, 2010). Given the intelligence and curiosity of these animals, such behaviour is not entirely unexpected. VIdeo Prior to Atack

Richard Ellis (2010), marine conservationist at the American Museum of Natural History, suggests, however, that this was not unnatural behaviour for a ‘predatory animal whose very nickname suggests it kills’, “When you’ve got a big predatory animal near warm-blooded prey, the possibility of attack is very high” (Haq, 2010).Richard Ellis Interview

Thus, while the likes of Ellis and other animal activists believe that it is wrong to cage animals train them for human amusement and who believe that it was only a matter of time before an unfortunate ‘accident’ of this nature would happen (Wood, 2010), there are yet others who attribute the cause of the problem to Tilly itself.

And while SeaWorld insists that Tilly will continue to be an important part of SeaWorld and cannot be re-released into the wild because it would die and is needed for research and breeding (Farber, 2010), there are still those who condemn the programme and who insist that orcas can be successfully reintegrated into the wild, as was done with Keiko, the animal star of the movie “Free Willy” (Wood, 2010; Farber, 2010).


Boy Survives Bump From Killer Whale. (2005, August 15). Retrieved April 5, 2010, from The Seattle Times:

Ellis, R. (2010, February 25). SeaWord Killer Whale Attack. Retrieved April 5, 2010, from The Washington Post:

Ex SeaWorld Official: Trainer Made Mistake. (2010, February 26). Retrieved April 5, 2010, from CBS News:

Farber, D. (2010, February 26). SeaWorld Defends Serial Killer Whale. Retrieved April 5, 2010, from CBS News:

Haq, H. (2010, February 25). SeaWorld Tragedy: How Common are ‘killer whale’ Attacks? Retrieved April 5, 2010, from The Christian Science Monitor:

Heimlich, S., & Boran, J. (2001). Killer Whales. Stillwater, MN: Voyageur Press.

Orca Shares the Waves with Local Surfer. (2008, September 12). Retrieved April 5, 2010, from 3 News:

SeaWorld Killer Whale Attacks Trainer: Latest in String of Deaths. (2010, February 25). Retrieved April 5, 2010, from Telegraph:

Whale Attack Renews Captive Animal Debate. (2010, March 1). Retrieved April 5, 2010, from CBS News:

Whale Trainer’s Family Speak of Shock at SeaWorld Death. (2010, February 25). Retrieved April 10, 2010, from BBC News:

Wood, D. B. (2010, February 24). Death of SeaWorld Trainer: Do ‘Killer Whales’ Belong in Theme Parks? . Retrieved April 5, 2010, from The Christian Science Monitor:

Body Snatchers

Upon watching a clip on entomopathogenic fungi, specifically Cordyceps unilateralis in my Evolution Psychology class, it set me thinking if all behaviour as exhibited by animals are indeed as “fitness” directed as we think.

Cordyceps: Attack of the killer fungi

 Horror buffs would be familiar with the idea of possession, which is quite literally what we see with Cordyceps unilateralis and its host – the carpenter ant. Upon infection, the fungus enters the body of the ant, and when it is ready to sporulate, affects the ant’s perception of pheromones through chemicals released by the fungus into the ant’s brain. The ant then exhibits highly atypical behaviour and climbs to the top of a plant stem where it anchors its mandibles and dies. The fungus feeds on the brain of the ant and sprouts as a stalk from the ant’s head which once mature, would explode, spreading its deadly spores yet again.

Sprouting Cordyceps

Sprouting Cordyceps


Straight out of a science fiction movie, whenever a colony member is discovered to be infected, it is immediately removed to a far away location from the rest. Such measures, while seemingly drastic, are necessary to prevent the death of entire colonies.

Perhaps more sinister would be the gordian worm, or Spinochordodes tellinii, which induces its host to “jump off the deep end”, literally drowning itself such that the worm, which may only emerge in water, can do so.

Gordian Worm and Friend

We’ve learnt of how genes may affect an individual’s behaviour, most saliently seen in psychological disorders such as schizophrenia. In the animal and plant world, the genes of such parasites as the  gordian worm and the cordyceps fungus, while encoded in their own genome, have a direct effect on their hosts’ behaviour; in what Richard Dawkins dubbed the extended phenotype. This then begs the question. The next time you sneeze while having the flu, are you sneezing as a reflex commonly thought to serve a “fitness” purpose in getting rid of an irritation in your nose? Or are you sneezing for the propagation of the virus?


Biron, D. G., et al. (2005). Behavioural manipulation in a grasshopper harbouring hairworm: a proteomics approach. Proc. R. Soc. B., 272, 2117-2126.

“Brainwashed by a parasite,” by Mo. Neurophilosophy, 20 November 2006. URL: (accessed on 3rd Apr 2010).

“Cordyceps: attack of the killer fungi – Planet Earth Attenborough BBC wildlife,” by BBCWorldwide Youtube Channel, 3rd November 2008. URL: (accessed on 3rd Apr 2010).

“Gordian Worm and Friend,” by VB Films, 2002.