40 THE SENSES OF ANIMALS 



which run through that area. It is a large frog, twice as big 

 as our Common Frog, and as it spends some of its time 

 basking on the banks in spring and summer (as well as being 

 submerged in the water) its feeding behaviour may be seen 

 under both conditions. The Marsh Frog is also nocturnal 

 and observations at night, if you are armed with a strong 

 electric torch, are well worth while. 



This frog does not move away from the vicinity of the 

 dykes and canals and it can be captured with a deep net 

 once its habits have been watched and if you are prepared 

 to be agile and quick yourself. You can easily see these frogs 

 feeding in the daytime if you can spot one and sit quietly 

 watching. On land the food of these frogs is varied : all kinds 

 of insects are taken, and the tremendous leaps that these 

 frogs sometimes make suggest that they have longer sight 

 than other less agile species. 



It is of course very difficult to make field observations 

 when the frogs are feeding under water ; but if some frogs 

 are captured and painlessly killed, examination of their 

 stomach contents will show that their underwater prey is as 

 varied — if not more varied — than that on land. I have taken 

 from the stomachs of Marsh Frogs such diverse organisms as 

 dragonfly larvae, water beetles, fresh-water shrimps, may- 

 fly nymphs, water spiders, newts, tadpoles (including those 

 of its own species) and on one occasion a two-inch young 

 Marsh Frog! Fish are also taken, and the late Malcolm 

 Smith records a fish of three inches in length. Now the point 

 here is that all these creatures move and some move very 

 quickly, yet the Marsh Frog, with the aid of its third eyelid, 

 can capture all these victims as easily under water as it can 

 on land with better light conditions. 



Toads are easier than frogs to experiment with; this is 

 largely due to their longer tongues and also their sluggish 

 movements which give one a better chance of assessing their 

 length of sight — their acuity would seem to be just as good 

 as frogs' and their angle of vision is, if anything, even better. 



I have experimented with both our Common and Natter- 

 jack Toads in the field and in captivity, and with many 

 foreign species also under captive conditions. I have not 

 found a great deal of difference in their seeing abilities except 



