MATING BEHAVIOR OF THE WOOD FROG. 



clasping the female. Each male strives to get into a more favor- 

 able position and (incidentally) to push off the other males. In 

 one mass the female was lying on one side with the head under 

 water and was apparently dead, while five males were holding 

 to her and to one another in various positions and several other 

 males were making occasional efforts to fasten hold on the bunch. 

 Another such mass was lifted out in a dip net and when separated 

 was found to consist of six males and the female. Five other 

 males had been attempting to take part in the struggle but were 

 not holding fast to the mass, avoided the net, and escaped. Some- 

 times the pairing female leaves the water but since she does not 

 stray far from the water's edge she is frequently followed by one 

 or more males. 



Copulation may continue for a day or two. Pairs were kept 

 in the laboratory together for thirty-six hours or longer. The 

 embrace is so strong that in forcibly dislodging the male one 

 fears lest the force employed must break the animal's leg. One 

 male was found clasping a small male green frog and another 

 late in the breeding season was found clutching a dead and some- 

 what decomposed female wood frog. 



The wood frog first appears at the ponds in spring after a 

 general thaw and several successive warm days. So far as 

 observed at the Cut-off Pond the mating season was from March 

 30 to April 4 in 191 1 ; March 28 to April 5 in 1912 ; and March 15 

 to 24 in 1913. It is possible that these do not represent the 

 extreme dates for the end of the season. In one other pond near 

 Cold Spring Harbor these frogs sometimes begin mating a day 

 or two before they do in the Cut-off Pond and in a third pond 

 wood frogs do noc appear for several days after the first eggs are 

 laid in the Cut-off Pond. Similar and much larger differences 

 in times of egg-laying, in these three ponds, are observed with 

 Ambystoma punctatum. These are presumably due entirely to 

 temperature differences at the different ponds. One of these 

 ponds is in a more sunny situation than the Cut-off Pond and 

 the other is on a north slope. 



The males apparently reach the pond first. In 1912 the chorus 

 was in full activity March 28. The pond contained little water 

 and there were perhaps 250 males in an area some 50 by 16 feet. 



