38 THE SENSES OF ANIMALS 



This incident was not only interesting as an example of the 

 way in which an amphibian can see and judge distance so 

 long as its intended prey is moving; it was also a lesson in 

 not always accepting as a rule statements made regarding the 

 activities of an animal. It proved that a Common Frog, in 

 spite of assertions to the contrary, can climb. 



Tree-frogs are also good subjects for observations on feed- 

 ing behaviour ; and any student travelling in countries where 

 tree-frogs are to be found can see their amazing ability to 

 focus an object which is itself moving while the frog is also 

 in motion. Moths which fly at dusk are very commonly eaten 

 by many species of tree-frogs, and if an observer provides 

 himself with an electric torch he will, with patience, be able 

 to watch tree-frogs launching themselves into the air to seize 

 a flying moth. It is true that they sometimes miss their prey, 

 but it is a cardinal error to imagine that predators always 

 make a satisfactory kill whether it be a lion attacking an 

 antelope or a tree-frog a moth. The fact that animals possess 

 senses far keener than our own does not rule out accident or 

 misjudgement. 



Should a student not be in a position to travel abroad, it 

 is still possible for the foregoing kind of observation to be 

 carried out with captive tree-frogs which not only do quite 

 well in suitable cages or tanks, but make most attractive 

 "pets" as well. 



Any cage or tank for tree-frogs must be roomy ; one for a 

 pair of frogs should be at least two feet in height, and not less 

 than eighteen inches in breadth and twelve inches long. 

 Some sand in the bottom with growing moss on top of it, a 

 pie-dish of water and some branches of a broad-leaved shrub 

 will be adequate — rhododendron or laurel is good. The tank 

 must have a perforated zinc cover to prevent escape and to 

 provide ventilation. 



I have at present a White's Tree-frog from Australia which 

 was adult when I first obtained it and which has lived and 

 thrived with me for over ten years. This large and handsome 

 bright green frog will give striking evidence of its keen sight 

 — both in daylight and at night. I have found that observa- 

 tions at night are the most impressive because, in addition to 

 demonstrating acuity of vision, they also indicate a very 



