The birds & the bees

2

The length in metres of scratch marks made by dinosaurs across four different Cretaceous sites in Colorado in the first known evidence of a type of mating-display behaviour known as “scraping”, much like that of modern-day birds.

15

The number of shark and ray species in aquariums that have been observed to practise parthenogenesis, or virgin birth. Instead of being fertilised by a male’s sperm, the animal’s own genetic material combine during cell division. 

32

The degrees Celsius above which a genetically male bearded dragon incubates to become a fully functional female, while still looking and acting like a male.

3 000

The average number of eggs a two-year-old humpy shrimp (Pandalus goniurus) lays as a female. These shrimps start off as male in their first year and then change sex.

8-10

The number of days it takes the ovaries of bluehead wrasse females to become sperm-producing testes. Bluehead wrasse live in schools made up of one dominant male and various females. The sex change happens in the largest female when the dominant male dies.

15

The length in centimetres of two of the tail feathers, tipped in iridescent “paddles”, of the marvellous spatuletail (a type of hummingbird). The feathers are almost twice as long as the bird’s body and are given a frenzied whip-around to impress females.

30

The number of weeks it takes some swamp eel hatchlings, which all start out female, to become male. Some of them become female again when there is a shortage of females.

5-6

The percentage of flowering plant species that are dioecious — that is, with separate “males” and “females”. Most plant species are monoecious, producing both sperm and eggs in a single plant.

1

The number of bees found so far that are half-male and half-female – this one was discovered in a beehive in Pittsburgh, Pennsylvania, and is thought to be the result of a rare genetic quirk.