Femoral pores are a part of aholocrinesecretory gland found on the inside of the thighs of certainlizards andamphisbaenians which releasespheromones to attract mates or mark territory. In certain species only the male has these pores and in other species, both sexes have them, with the male's being larger.[1] Femoral pores appear as a series of pits or holes within a row of scales on the ventral portion of the animal's thigh.
Femoral pores are present in allgenera in the familiesCordylidae,Crotaphytidae,Hoplocercidae,Iguanidae,Phrynosomatidae, andXantusiidae.[1] They are absent in all genera in theAnguidae,Chamaeleonidae,Dibamidae,Helodermatidae,Scincidae,Xenosauridae, andVaranidae families.[1] They are present in other lizards and amphisbaenians quite variably, some geckoes,Phelsuma, for example have these pores, others in the same family do not.[1]
In thedesert iguana (Dipsosaurus dorsalis), the waxylipids released from the femoral pores absorbultraviolet (UV) wavelengths making them visible to species which can detect UV light.[3] According to tests performed on theGreen iguana, the variation in the chemicals released by the femoral pores can help to determine age, sex, and individual identity of the animal in question.[4] Maleleopard geckos (Eublepharis macularius), actually taste the secretions by flicking their tongues, if a male determines the other gecko in question is a male, the two will fight.[5]
In certain species such as geckoes, the females lack femoral pores altogether. In most families of lizards that have femoral pores, notably the iguanids, both sexes have femoral pores, but the males tend to be much larger than females of the same size and age.[4] In these instances they are used as a marker forsexual dimorphism.[4]
The number of femoral pores varies considerably among species.[2] For example, the number of pores in male lizards of the family Lacertidae can range between zero (e.g.Meroles anchietae) and 32 (e.g.Gallotia galloti) per limb.[6] Also, shrub-climbing species tend to have fewer femoral pores than species inhabiting other substrates (such as sandy and rocky substrate), suggesting a role of the environment on the evolution of the chemical signaling apparatus in lacertid lizards.[6]