But again surprises await us. Many frogs and toads, both the mothers and the fathers, show a really marked development of the familial instincts.[18] An illustration of this care is furnished by a large tree-frog (Hyla faber) of Brazil, commonly known as the Ferreiro, “the smith,” from its strange voice resembling the mallet of a smith, slowly and regularly striking on a metal plate. This frog prepares a nursery in the shallow waters of the ponds, where a basin-shaped hollow is dug in the mud. The building is done by the mother, the material removed being used to form a wall, circular in shape, which is carried up to the surface of the water. In this cavity the eggs are placed, protected against the attacks of aquatic insects and fishes. A Japanese tree frog (Rhacophorus schlegelii) builds a similar nest, but here the mother lines the walls of her nursery with a secretion, a kind of milk food, from her own body, which by rapid movements of her feet is worked into a froth, and in the midst of this foamy mass the eggs are laid. More remarkable is the nursery building of the “Wollunnkukk” frog (Phyllomedusa hypochondrialis) of Paraguay, whose habits were noted by Dr. Budgett during the exploration of the Paraguayan Chaco. “Whilst sitting near the water’s edge he saw a female carrying a male upon her back. At last she climbed up the stem of a plant, reached out and caught hold of an overhanging leaf and climbed on to it. Both then caught hold of its edges and held them together; and into the funnel thus formed the female poured her eggs, the male fertilising them as they passed. The jelly surrounding the eggs served as a cement to hold the edges of the leaves together. Then, moving up a little further, the process was repeated until the leaf was full, and about a hundred eggs had been enclosed.”[19]
A similar leaf nest is made by a Brazilian frog, known as Ihering’s frog (P. Iheringí), while a home of more elaborate construction, in which several leaves are used, is prepared by Savage’s leaf-frog (P. Sauvagii).
It should be noted that in these cases the care of the parents is confined to the providing of a nursery; when once this is done the young are abandoned. But many frogs and toads do much more than this, and one or other parents, most often the father, guard their offspring with jealous care. A Papuan frog-father, for instance, takes up the duties of a nurse; and when the eggs are laid, he sits upon them, holding the mass with both hands. And this vigil he keeps during the whole time while the young are undergoing growth, passing through the larval and tadpole stage.
We must own that such a father acts with singular devotion. It should be noted that seventeen eggs only are laid by the mother, a much smaller number than is common among the species where neither parent affords any kind of guardianship. This is what we should expect. Nature has different ways of gaining the same end. Life must be carried on, that is all that matters—an incessant renewal, an undying fresh beginning and unfolding of life. But a species is maintained sometimes by the prodigality of production and sometimes by the expenditure of care and sacrifice on the part of the parents. And here we find again a lesson waiting for us to learn. For it is hardly necessary to point out that the same facts are true of human births; just as the family is unregulated or considered, do we find waste and many births with parental neglect in the first case and restricted births with parental devotion in the second. There seem to be no problems of the family that these pre-human parents have not had to face and solve.
But to return.
“The celebrated Midwife toad (Alytes obstetricans) gives us a further delightful example of the father nursing the young. The mother-toad lays her eggs attached to one another by threads so that they form a long chain. The father-toad then twines this chaplet of his wife’s eggs round and round his thighs. He has the strange appearance, it has been said, of a gentleman of the court of the time of James I, arrayed in puffed breeches. His devotion is very complete. After having encumbered himself with the coming family, he retreats to a hole in the ground. Here he stays with admirable patience by day, stealing forth at night to feed, and to bathe his egg-burdened legs in dew or, when possible, in water. When his period of service is past and the young are ready for quitting the eggs, he seeks the water. Here before long the young burst forth and swim away, whereupon the father, now free from his family duties, makes himself tidy (cleans himself of the remains of the eggs) and resumes his normal appearance.”
With some frogs, as, for example, in certain S. American and African species, the parents take up the burden of caring for the young only after they have reached the tadpole stage. The German naturalist Brauer recently found in the Seychelles islands a small frog (Arthroleptis Seychellensis) undertaking the guardianship of the young family. An adult frog (it is not stated whether it was the father or the mother) was carrying nine tadpoles on its back, to which they were attached by a sucker on the belly. Unfortunately, little is known of the habits of these frogs. It is believed that the eggs are laid in some shallow pool, and that later one or other parent returns to the nursery to take up the care of the young tadpoles.
A further remarkable case of care exercised by the father is that of Darwin’s frog, the Rhinoderma darwini, where the eggs are guarded in a great pouch under the throat, and opening by two slits into the mouth. During the courtship this pouch is used as a voice organ to charm the female, with sharp ringing notes like a bell. But the love-calls end with the birth of the family. There is now serious work to be accomplished. The father takes his wife’s eggs into his pouch, which now enlarges and extends backwards under the belly to the groin, and upwards on each side almost to the backbone. In the warm chamber thus formed, the tadpoles live until they become young frogs. They then make their way up through the doorways into their father’s mouth, and from that living nursery they swim out into the wide world.
Well, what can we say of this case? We have heard of some animal fathers eating their progeny, but here the father’s mouth is turned into the hatching nursery. Did I not tell you we should find very much to astonish us?