Chemicals that disrupt hormones are having a detrimental effect on male animals, according to a new report.
The study, from the CHEM Trust, found that synthetic chemicals in the environment are causing problems among male mammals such as abnormal, undescended or undersized testes.
Soil, air and water-based male animals are being affected.
In egg laying species, such as fish, birds and reptiles, males have been found to be producing egg yolk protein, usually a reserve of the female.
Otters in the UK, polar bears in the Arctic and land antelopes in Africa have all been found to be affected by the
environmental analysis.
Man-made chemicals, it is claimed, can harm male animals by blocking the production and action of androgens.
Supported financially by WWF-UK and Greenpeace, CHEM Trust aims to create "a world where humans and wildlife co-exist with a sustainable chemical industry".
The organisation also works to replace harmful man-made chemicals with "safer alternatives".