larger prey. Insectivores have an enhanced dependence on vertebrate food material, which is larger and more dangerous than their power to weight ratio would allow, thus requiring an extra asset to overcome these difficulties. Extant shrews do not have specialized venom delivery apparatus. Their teeth do not have channels, but a concavity on the first incisors may collect and transmit saliva from the submaxillary ducts, which open near the base of these teeth. The European mole (Talpa europaea), and possibly other species of mole, have toxins in their saliva that can paralyze earthworms, allowing the moles to store them alive for later consumption. Male platypus Both male and female platypuses (Ornithorhyncus anatinus) hatch with keratinised spurs on the hind limbs, although the females lose these during development. The spurs are connected to the venom-producing crural glands, forming the crural system. During the mating season these glands become highly active, producing venom to be delivered by the channeled spur. Echidnas, the other monotremes, have spurs but no functional venom glands. Although not potent enough to be lethal to humans, platypus venom is nevertheless so excruciating that victims may sometimes be temporarily incapacitated. Platypus envenomation was fairly common when the animal was still hunted for its fur. Nowadays any close contact with the animal is rare and restricted to biologists, zookeepers and anglers (who occasionally catch them in fishing lines or nets). When platypuses attack, they drive their hind legs together with considerable force so that the spurs are embedded in the flesh caught between and if venom is being produced, a few milliliters are injected by repeated jabbing. The spurs have enough strength to support the weight of the platypus, which often hangs from the victim, requiring assistance for removal. Most of the evidence now supports the proposition that the venom system is used by males on one another as a weapon when competing for females, taking part in sexual selection. During this season, males become more aggressive and are found with punctures in their bodies, especially in the tail region. Adult male platypuses largely avoid each other, outside of this mating rivalry. Platypus venom is likely retained from its distant non-monotreme ancestors, being the last living example of what was once a common characteristic among mammals. Fossil records show that venom delivery systems were not sexually dimorphic in ancestral monotremes. It has been hypothesized that venom spurs were once used