How do you tell if a western fence lizard is carrying eggs?

This depends on the type of lizard it is, but there are some general rules that apply to many species.

Female lizards tend to be longer and slimmer than males, lighter in weight, and have a smaller head than the males. In some species, the male is more brightly coloured, in order to attract the female, and often certain markings such as coloured throats will become more pronounced in colour during breeding season.

When looking at the underside of the lizard, males have a small bulge between the end of the abdomen and the tail. Also, the appearance of the femoral pores is different. Femoral pores are small openings lining the bottom of a lizard's legs. In males, they are located near the bulge at te base of the tail, generally in a 'V' shape, and darker in colour than the surrounding scaly skin. Female femoral pores cannot be seen as easily.