Sexual dimorphism: why males and females differ

In biology, sexual dimorphism refers to the physical or behavioural differences between males and females of the same species. These differences can range from size and weight to colour, scent, or behaviour. For hedgehogs and tenrecs, sexual dimorphism is generally subtle compared to some other mammals, but it is still important for understanding breeding, behaviour, and husbandry.

Hedgehogs

Physical differences
Hedgehogs show little external dimorphism. Males and females are nearly identical in colour, spine pattern, and overall body shape. The easiest way to tell them apart is by examining the position of the genital opening:

• In males, the penile sheath is located mid-abdomen and looks like a small “belly button.”
• In females, the genital opening is much closer to the anus.

Size differences are minor. Some females may appear slightly larger due to pregnancy or weight gain, but in general males and females overlap in weight and size ranges.

Behavioural differences
During breeding season, males are more active and may roam more in search of mates. Females may become more defensive when pregnant or nursing, and their behaviour is strongly influenced by maternal instincts. Outside breeding, both sexes are solitary and territorial, with no clear dimorphic differences.

Tenrecs

Tenrecs, being a highly diverse family, show more variety in sexual dimorphism across species.

Physical differences
In some species, males are noticeably larger than females (for example, in certain larger spiny tenrecs). Male reproductive organs are often more visible than in hedgehogs, though exact features vary by species. In smaller tenrec species like the Lesser Hedgehog Tenrec (Echinops telfairi), size overlap between sexes is common, and external dimorphism is minimal.

Behavioural differences

• Males may become more territorial or aggressive during the breeding season.
• Females usually show stronger nesting behaviour: gathering materials, digging, and defending their young.

Some species demonstrate seasonal dimorphism: outside of the breeding season, testes in males shrink dramatically, making them less obvious. This makes it harder to determine sex outside reproductive periods.

Why Do These Differences Exist?

Sexual dimorphism arises because males and females play different roles in reproduction and survival:

• Reproductive investment: Females invest heavily in gestation and lactation, so their physiology and behaviour adapt to protect and raise offspring.
• Mate competition: Males often compete for access to females, leading to behaviours such as roaming, scent-marking, or aggression.
• easonal cycles: In tenrecs, reproduction is strongly tied to environmental conditions in Madagascar (rainy vs dry seasons), which shapes their sexual traits across the year.

In Summary

Hedgehogs show very limited sexual dimorphism, with sex determined mainly by genital position rather than obvious physical traits. Tenrecs, by contrast, show more variation: some species have noticeable size differences, and many display seasonal reproductive traits. In both groups, behavioural dimorphism is most apparent during the breeding season, when males become more active or competitive and females focus on nesting and rearing young.