Museum of Natural History
Snakes and Lizards
Location: Main Court, Lizards, Snakes, and the Tuatara Case
There are many organisms capable of reproducing without fertilisation of egg cells by sperm. This process, known as parthenogenesis, is rare in vertebrate animals, but it is found in some species of reptiles. In particular, some species of Whiptail Lizards (Aspidoscelis uniparens, not displayed here) are entirely female – there are no males. This is thought to be due to hybridisation between different species of Whiptail Lizards.
As there are no males, there is no exchange of gametes or male-female sexual behaviour. Nonetheless, sexual behaviour is observed in these lizards, even though it does not contribute to sexual reproduction. This makes the Whiptail Lizard one of the few animals with well documented same-sex sexual behaviour. This behaviour goes beyond displays or occasional occurrences – ‘mating’ between females is regularly observed. Whiptail Lizards are therefore an important part of the study of same-sex behaviours in the natural world.
Striped Hyaena taxidermy
Scientific name: Hyaena hyaena
Location: Main Court, Mammals of Africa Case
The anatomy of a relative of the Striped Hyaena, the Spotted Hyaena (Crocuta crocuta), is unique. Females possess an enlarged clitoris which contains the channels through which they urinate, copulate and give birth. While this prevents the occurrence of sexual coercion by males, the anatomy of the clitoris can lead to complications – 15% of females die during their first birth and 60% of firstborn young die. Before thorough research was undertaken, it was assumed that all Spotted Hyaenas were born with a penis and that many individuals were hermaphrodites. This has now been shown to be incorrect.
Clitoral licking amongst Spotted Hyaena females is a common social behaviour thought to help strengthen social bonds, with lower ranking individuals licking the clitoris of higher ranking individuals in greeting. Penile licking does not occur due to the low rank of males. This behaviour illustrates the importance of questioning the hetero-normative biases of human society and shows the sexual diversity present in the natural world.
Bluehead Wrasse cast
Scientific name: Thalassoma bifasciatum
Location: Main Court, Euteleosts (fish diversity display)
The Bluehead Wrasse fish is an important example of non-standard biological sex in nature. When aging, even after sexual maturity, some females may transition to become breeding males. The Bluehead Wrasse is not the only fish species to change sex. Some species of clownfish exhibit similar behaviour, with individuals changing from male to female. (Nemo’s father should have become his mother in the popular Pixar movie!) The Wrasse are not born with both male and female anatomy, but they change from one sex to the other in order to maintain a gender balance necessary for population stability. This process is called sequential hermaphroditism.
As with the human transgender population the transition is neither a decision nor choice they make. These sex changes are due to the levels of hormones in the environment, based upon the ratios between the sexes of Wrasse. A similar process is thought to be responsible for transgenderism in humans, but in this case due to the hormonal environment in the womb during development.
Scientific name: Giraffa camelopardis
Location: Main Court, Skeleton Parade
Out of the approximately 1500 species of animal that have been identified as displaying same-sex behaviour, the giraffe is one of the most studied. Males have been documented rubbing their necks on one another’s bodies (‘necking’), heads, necks, loins and thighs before engaging in same-sex mounting. In fact, these engagements occur more frequently than male-female mounting, which only accounts for 7% of all observations. One in 20 male giraffes are believed to be necking another male at any given time. Observing their interactions helps us understand that homosexuality is not just prevalent in humans. Sexuality is just as non-binary or fluid in animals. The sexual behaviour of giraffes shows us that homosexuality is a normal occurrence in our world.
Giant African Land Snail
Scientific name: Achatina achatina
Location: Main Court, Mollusca displays
Up to 30cm in length and 32g in weight, the giant African Land Snail is a simultaneous hermaphrodite, meaning that it has a full set of male and female reproductive organs at the same time. The snails mate by exchanging sperm between each other, with the larger snail sometimes acting as the ‘female’ receiving the sperm. During courtship the snails try to shoot one or more ‘love darts’ into the prospective mate. This introduces a substance that aids the sperm’s survival and helps in the production of between 100 and 500 eggs that can be stored inside the snails’ bodies for up to two years. Living between three to five years the snails produce clutches of eggs every 2-3 months. It is an important source of protein among some West African groups, but its success has also resulted in it becoming a pest and adversely affecting agriculture, ecosystems and human health. It is the most frequently occurring invasive snail species worldwide.
Hive of Honey Bees
Honey Bees are an interesting case. They have three classes: a female queen, female workers and male drones. However, their sexes cannot be compared or categorised in the same way that they are for mammals. The 'male' bees develop from unfertilised eggs and are, in effect, females with only one set of chromosomes. This is very different to what may be perceived as the 'normal’ male and female gender-binary. It could be considered that there is actually only one sex of honey bee, with some bees never reaching full development.
Examples like this in nature are important. It is simple to define humans as having male or female sex and a corresponding gender, and then to classify any folk who bend or deviate from that single, pre-defined gender as odd and freakish. However, nature shows that sex and gender variation are not unusual. Maybe it is time to think outside the box!