Nest Watch – 3

Geetha Iyer

In this concluding part of Nest watch, I have an assorted collection of nests that are quite different from what one is accustomed to seeing or hearing about. I am describing these nests in the fond hope that when teachers take students on eco-tours into protected sanctuaries, they can look out for these nests.

Wild pigs
We know them as wild boars. Recently they have been rechristened by biologists as wild pigs. These are animals that are easy to observe in the forests although the loss of habitats is fast posing a threat to survival of these creatures. Once upon a time there were at least six to seven species of wild boars roaming the forests of India. Today there are just two species left – the wild pig and an even more endangered pygmy hog found in the north-eastern regions of our country. Generally nocturnal, they possess a strong sense of smell but poor eyesight. They are not scared of humans, are known to destroy farm crops and come looking for left over foods around human habitation. They roam about in groups-described as sounders – which consist of the mature sow, sub-adult sows, and young ones. The males are generally solitary and enter the sounder during the mating period. The wild pigs are quite brave and will charge at you at the slightest hint of insecurity; they charge even at a tiger if they sense danger. Offence it seems is their defence, so be careful when you see them.

There are two kinds of nests that the wild pigs make. The farrowing (for giving birth) and the resting nests. The pre-parturition nest or the farrow nest is made by the sow 24 hours before giving birth. The nest is made of plant materials available close to where the nests would be built. The nest is a length wise structure generally oval to oblong in shape. These are made in select places chosen by the female. The selected place is generally first dug out by the females before the construction starts. The depressions are lined with leaves and are generally built next to trees or wooden logs for added protection. Depending on the weather sometimes they are built in open grasslands or next to water. The nest often resembles a long bed of woven basket. The top of the nest is like a dome to cover and keep the babies warm. A bigger and larger sow often builds a bigger nest than the smaller sows.

The farrowing nests are used for only a week after which they are shifted to a resting nest. The nests, besides providing warmth to the newborns are believed to also protect it from predators such as leopards, when the sow is away foraging. She never moves far away from the young ones, but the danger of a predator is high. Thus the farrowing nests are constructed to serve as a camouflage too.

The resting nest is not as complex as the farrowing nest. However it is not sometimes possible to distinguish the two as noted by researchers who examined several farrow and resting nests.

In general, these are used, as the name suggests, by resting females and hence do not posses all the characteristics of a farrowing nest. Sometimes the excavations were shallow, often linings were scarce with just the bedding materials arranged sufficiently to allow the pigs to rest.

Do domesticated sows that are provided with shelters build nests? The curiosity sparked an experiment and a sow that had littered for two years was provided with nesting materials in her pen a week before she was expected to litter. The video shows how all the characteristics shown by the sows in the wild were still operational and present in domesticated ones too. She used the materials just as the sows in the wild and 24 hours before giving birth she built the nest with the materials provided, lining the nest carefully and laying out the material much in the same fashion as seen in the wild . It is indeed remarkable evidence of what ethologists often refer to as instinctive behaviour imprinted in the organism’s system.

King cobra
One generally does not associate nest building with snakes. We would wonder how can they build when they have no limbs to engage in such a complex activity? I am fairly sure no snake ever feels the lack of limbs as a disadvantage. The king cobra is the only snake that builds a nest. The females are caring mothers who not only build a nest for the eggs to incubate but also stay and guard the nest till the hatchlings emerge. Once the young ones come out, or just before hatchlings emerge, her duty completed, the mother cobra leaves the nest. This is an instinctive behaviour to ensure that the hatchlings she so carefully guarded do not end up as her meal.

I have not personally seen the King cobra build a nest, but have seen an empty nest. The females build the nest using plant materials such as leaves, twigs, etc. Externally the nest may not appear to have a definable design, appearing like a heap of partially drying vegetation; however examine it after the nest has been vacated and you will see that it is a carefully constructed nest of two storeys. The ground floor or the lower chamber is a shallow but wide pit in which eggs are laid. This is covered by leaf litter and the vegetation piled above this forms the upper storey on which the King will lie guarding the eggs. She gathers the material required for her nest by moving her body around loose leaf litter till they form a pile. The decomposing vegetation that
covers the lower chamber provides the temperature necessary for the eggs to hatch. It is indeed an indication of the intelligence exhibited by the snake – to be able to build a nest of such pragmatic yet complex design to ensure that the natural process provides heat for incubation; while she herself ensures that no predator or others mistakenly trample the heap or poach the eggs.

Normally a clutch may contain anywhere between 20-50 eggs which are laid during the months of April – June. The parental care ceases with the emergence of the young which then is at the mercy of a variety of predators ranging from ants, centipedes to civets, and mongooses. It is perhaps for this reason, to defend itself that the newly hatched king cobras also have the same strong venom as adults.

Termite
What’s new about a termite nest, you might well ask! One associates high citadels of mud with the termites, but these master architects of the insect world build nests that you wouldn’t ever think is theirs. You would probably avoid an oval jackfruit size structure stuck to a tree, if you ever saw one. It could well be thought of as a hornet’s nest. I too did the same. But the lack of any activity on the outside sparked my curiosity. On closer inspection, it revealed a surprise. When I gently tapped the surface of the nest, it crumbled, revealing chambers within and an immediate appearance of the worker termites to explore and repair.

Termites build a variety of nests although most naturalists talk only about those long ones jutting out of the ground. This particular nest is referred to as carton nest and is generally spherical to ellipsoidal in shape. Any damage to the exterior is promptly repaired by the workers. The cells that surround the queen are specially reinforced to protect her and her cell is usually found close to the tree trunk to which the entire nest is attached.

Ants

We see them scampering away on the soil, also know that they come out in hoards from the soil during the rains transferring their pupae from one place beneath the ground to another. But relatively less known is the fact that there are many ants that build nests. You can read in detail how some of these nests are constructed using silk in my book, The Weavers-the curious world of insects (Read a review in the November 2016 issue of Teacher Plus).

There are many different kinds of nests that ants build. Although wasps, hornets, and termites take away all the attention for being the greatest architects, ants are by no means less able when it comes to building nests. Here, I confine myself to one such species that does not use silk, but demonstrates how clever and adaptable ants are. Tree ants belonging to the genus Crematogaster build nests on trees. When you take students on eco-tours, be sure to look out for these on trees. Some refer to these ants as acrobat ants. Their nests described as carton nests are spheroidal in shape. They are built on trees, at the junction of a branch, enclosing two or three twigs that seem to function like a foundational support for the nest. These are built for the purpose of raising their brood. Hence you will find several chambers for the same. These nests have several layers sloping downwards, thus ensuring that during the rains, water does not enter the chambers.

The nest is made of several sets of carton shaped structures built one above the other. The material used to build these nests are well-chewed plant materials mixed with soil. These sturdy nests built on trees are capable of withstanding wind and rain. Some species of Crematogaster will not build new nests but occupy the termite nest I described above and modify it to suit its purpose.

But just as they occupy the termite nests, the new nests that some species built are in turn occupied by birds. The rufous woodpecker uses the tree ant’s nest as its own when it has to raise its brood. When it is time for the woodpecker to nest it will open the ant’s nest to carve out a chamber in the centre of the nest to lay its eggs. The ant nest being roughly the size of a football, there seems to be enough space for both the species to coexist. Their relationship is interesting. Ants love the bird’s eggs and the bird feeds on ants. Yet neither feeds on the other while raising their respective broods. The ants do not attack the woodpecker despite some ant larvae being destroyed when the woodpecker builds its nest. After the bird has laid its eggs, it protects the nest from other woodpeckers, not allowing them to use any other part of this nest. It also does not eat any of the ants of this colony. The world of animals has many such examples of how cooperation is a relationship favoured over competition.

Some of the nests seen among invertebrates are examples of sublime art and creativity. Do we have the time and patience to observe them? If we did, we would discover a whole new world of architecture to learn from. I have not included Paper wasp nest nests built by different families of wasps, hornets, beetles, orthopterans or several other families of insects, other invertebrates and vertebrates. But I do hope I have kindled some curiosity to explore the world of nests among animals. It’s a project students of all ages will enjoy doing.

References

1. https://www.youtube.com/watch?v=XD2TgitLPU8 – Wild sow building a nest
2. https://www.youtube.com/watch?v=gnlhx75UMfc domesticated sow exhibiting the same behaviour
3. Differences in nest architecture between the neotropical arboreal termites Nasutitermes corniger and Nasutitermes ephratae (ISOPTERA: TERMITIDAE) BY Barbara L. THORNE https://www.hindawi.com/journals/psyche/1980/012305/abs/
4. https://www.researchgate.net/publication/261256426_Architecture_of_arboreal_nests_of_crematogaster_ants – Research article on Tree ant nest

The author is a consultant for science and environment education. She can be reached at scopsowl@gmail.com.