HIGHER CHOROATES 



281 



Owing to climatic conditions, North America's 

 amphibian activity varies throughout the year. The 

 activity peaks in the spring (the breeding season), 

 becomes low in the summer, rises in the fall, and 

 drops again in the winter. 



These seemingly unimportant animals like almost 

 any group of animals are a major environmental force 

 in their habitats. They are mainly carnivorous, feed- 

 ing upon various smaller animals; in turn, they are 

 eaten by certain fishes, snakes, birds, mammals, and 

 invertebrates. They contribute to soil' formation by 

 burrowing into and aerating the soil and by adding 

 humus to developing soil. Their eggs provide habitats 

 for certain green flagellates and hosts for certain 

 parasitic fungi. Their bodies (mainly through 

 moisture loss and body mass) influence environmen- 

 tal temperature, moisture, light, and wind in re- 

 stricted areas. 



Very few amphibians have specialized food habits; 

 their food habits are generalized and resemble those 

 of many other animals. Amphibian diet is dependent 

 mostly upon the size of the animal and its method of 

 getting food, the habitat in which it lives and hunts 

 for its prey, and the relative abundance and size of 

 food organisms available when the amphibian feeds. 

 Within these very general and minor limitations, 

 there are seasonal and age changes in food intake. 

 Seasonal changes are associated with seasonal abun- 

 dance of prey and seasonal movements of amphibians 

 and prey from habitat to habitat. Age, or life cycle, 

 changes in food are typical, even when larval and 

 adult food habits are much the same. Such changes 

 normally occur as a result of differences in size among 

 the various age groups. In addition, these different 

 age feeding habits must be considered of some sur- 

 vival value, because the different age groups within a 

 species show little competition for the same food. In 

 conclusion, amphibian food habits are very gener- 

 alized, but show sufficient differences among age 

 groups to be of benefit to individual species. 



Amphibian food is located by fairly simple sensory 

 mechanisms. In aquatic forms, sight, chemical recep- 

 tion, touch, and vibration reception are the primary 

 mechanisms. Aquatic individuals use these senses 

 to seek or become alert when waiting for possible 

 prey. Land forms tend to use vision, smell, and 

 "hearing" to locate and then to seek or await possible 

 prey. 



Upon locating food, amphibians take their prey in 

 different ways. Aquatic amphibians use their teeth 

 to seize their prey or merely engulf the prey with 



water and swallow the prey after expelling the water. 

 Those amphibians using their teeth may simply 

 swallow prey, first crushing it with the teeth; with 

 larger prey, the amphibians may first dismember it 

 by shaking, rotating it and their own bodies, or by 

 pressing the prey against the substrate. Terrestrial 

 amphibians with small tongues may use much the 

 same methods as aquatic forms. However, those land 

 species with large, fleshy tongues flick out their 

 tongues and capture their prey with a sticky mucus 

 secretion on the tongue. Smaller food is merely swal- 

 lowed, but larger food is crushed with the teeth, torn 

 with the aid of the feet, or pressed against the sub- 

 strate. Land amphibians either stalk their potential 

 food or wait for it to come within reach. 



ORDER GYMNOPHIONA {= APODA) (Caecilians) 



Diagnosis: worm-like, without legs or leg girdles, 

 tail short to absent; skin smooth and moist, glands 

 including some that eject an irritant; skin transversely 

 folded, some species have scales embedded in the skin 

 at the base of the folds; tropical, invertebrate preda- 

 tors, and moist ground burrowers; reproduction 

 typically with internal fertilization, eggs laid near 

 water or retained, larva aquatic or developing in 

 egg (Figure 16.16). 



Figure 16.16 A caecilian or "blind worm," Caecitia (to about 18 

 inches long). 



ORDER TRACHYSTOMATA (Sirens) 



Diagnosis: eel- or snake-like, body with distinct 

 head, trunk, and tail, all with two anterior legs only; 

 skin smooth and moist, without scales; fertilization 

 probably external; eggs laid in water; larvae aquatic 



