By Sean O’Donnell, Ph.D.

All photographs by Jana Reintjes

Based on the short communication “Predation on nests of three species of Amazon River turtles (Podocnemis) by underground-foraging army ants (Labidus coecus)” by Da Costa Reis M., Reintjes J., Chen D. and O’Donnell S. in Insectes Sociaux.

East of the northern Ucayali River in Peru is a geologically subsiding basin crossed by winding rivers and extensive wetlands. Much of this topographically flat region is flooded for several months annually by seasonal heavy rains. In this basin is the privately owned and managed Tapiche Reserve, a protected area of about 6000 ha that spans the Tapiche River. The reserve “land” is mostly under water at least two meters deep during the flood season. When the waters retreat, sandy beaches on the Tapiche River edges are visited by females of three species of Amazon river turtles (genus Podocnemis). Like sea turtles, Amazon river turtles lay their eggs in nests dug into beach soils.

Turtle eggs are subject to heavy human poaching on the Tapiche River, so the Tapiche Reserve staff (co-authors Murilo Reis, Jana Reintjes and Deborah Chen) have run a river turtle rescue and head-start program annually since 2012. They collect eggs from the reserve’s beaches and rear them in a guarded hatchery built on a beach at the reserve lodge. Eggs are placed in artificial nests in the hatchery, dug to dimensions that match the natural turtle nests. 

Turtle egg rescue efforts were especially successful in 2020. Over 9000 eggs were collected from 240 nests of three species of Amazon River Turtles, including the first nests of the critically endangered Giant Amazon River Turtle recorded in the area. Unfortunately, in fall 2020, the hatchery was attacked by subterranean army ants (Labidus coecus). The ants entered the nests by tunneling from below. The ant raid, never visible from the surface, was impressive in its extent and its persistence. Many thousands of polymorphic L. coecus workers were observed when the turtle nests were checked over the course of nine days in October; we believe the raid was continuously active throughout this period. The army ant raid grew in intensity over time and turtle mortality in one section of the hatchery, which contained the youngest turtles, approached 90%.

Paleotropical driver ants (genus Dorylus) regularly attack and consume vertebrates (Gotwald 1995), but it is often assumed that the blunt, non-crossing mandibles of Neotropical army ant workers preclude piercing of vertebrate skin and predation on vertebrates. Our paper adds to a growing literature suggesting vertebrates are on Latin American army ant menus more often than has been recognized (O’Donnell et al. 2005; Sazima 2017; López-Martínez et al. 2020). Relatively immobile vertebrates (including eggs and nestlings) may be especially vulnerable to Neotropical army ant predation. Larger-bodied L. coecus workers have impressive muscle-filled head capsules and large mandibles. Our observations suggested the ants entered turtle eggs and were also able to access hatchlings’ body cavities via soft tissues such as the eyes and yolk sacks. Army ant venom may also be relevant. Hatchlings that were stung by L. coecus workers appeared to be temporarily paralyzed, and some turtles died after being stung.

            The L. coecus raid on riverside turtle nests raises interesting questions about access to the Tapiche beaches by mobile subterranean ant colonies. A small area around the lodge remains marginally above water (all of the soil is saturated) at the height of the flood season, but there are few other patches of land within several kilometers in all directions. There are two possibilities to explain a Labidus raid reaching the lodge beach: either these usually subterranean ants have some way of persisting in the area through the flood, perhaps by moving into trees or rotten logs above the water level, or the ants traveled several kilometers underground from the nearest dry land to reach the banks of the Tapiche River.   

Army ant behavior present challenges for preventing predation on natural turtle nests and hatcheries. Army ant raids are massive and mobile, but some species such as L. coecus can raid continually for several days against rich food resources. Turtle nests in clusters on a beach or in a hatchery can suffer extensive damage from an army ant raid. Constructing hatcheries to prevent ant worker access from the soil beneath may discourage army ant predation, as long as abiotic conditions appropriate for turtle development can be maintained.

References

Gotwald Jr, W.H. 1995. Army ants: the biology of social predation. Cornell University Press.

López-Martínez GA,  Rondón-Zabala JI, Martínez-Parales E, Moya-Arévalo RH, Rodríguez OA (2020) Depredacion por insectos de nidos y neonates protegidos de Podocnemis vogli (sabanas inundables del Casanare). Acta Biol Colom 25:354-358.

O’Donnell, S., M. Kaspari, J. Lattke. 2005. Extraordinary predation by the Neotropical army ant Cheliomyrmex andicola: Implications for the evolution of the army ant syndrome. Biotropica 37: 706-709.

Sazima I (2017) New World Army Ants Eciton burchellii kill and consume leaf-litter inhabiting lizards in the Atlantic Forest, Southeast Brazil. Trop Nat Hist 17:119-122.

You can read Ajay’s recent research article about x-ray tomography to compare construction properties of the nests of wood-feeding and fungus-growing termite species here.

IS: Who are you, and what do you do?

Hi, I am Ajay Kumar Harit and are presently working as a Research Associate -III at the School of Environmental Science, Mahatma Gandhi University, PD Hills, Kottayam, Kerala, India. I have been studying termite biology, behaviour, and its influence on natural ecosystems and society for over 14 years. During this tenure, I was part of several national and international funded projects related to termites. I will continue exploring the special attributes of termites for as long as possible.  

IS: How did you develop an interest in your research?

I have started my journey with termites 2007 onwards as my Master of Philosophy (MPhil) dissertation work and it has been going on until now. I obtained my Master degree (MSc) in Zoology with specialisation in entomology, but build-up my interest in termite research after my MPhil degree when I gathered more knowledge about termites and their importance in nature.

IS: What is your favorite social insect, and why?

Termites, because they are one of the oldest social insects and are well-developed, highly systematic, and civilized. They play a significant role in soil and nutrient dynamics in the natural forest ecosystem. The unique quality of termites is the degradation of lignocellulosic waste (only this insect has this capability). Termites are also globally used as medicine by some of the ethnic communities. They are also consumed by human beings and other animals as they contain high-quality protein. 

IS: What is the best moment/discovery in your research so far? What made it so memorable?

I personally felt, my entire research journey is memorable, each and every moment has its own story to express.  Although for me, most memorable and challenging was the Ex-situ development (Rearing/culturing) of termite colonies under laboratory condition and its application in degradation of lignocellulosic waste, which I achieved during my doctoral work. 

In my career, culturing of termites in the laboratory and observing the first batch of termite eggs in my culture was the best moment of my research (that day I was the happiest person in my department), and has given me immense pleasure as well as the confidence to pursue and complete my research work.  

IS: Do you teach or do outreach/science communication? How do you incorporate your research into these areas?

Truly, I do not do it directly or in a systematic approach, but I do it indirectly when sharing my findings with my teachers, colleagues, friends, students and scientific social network sites such as Research Gate, Academia, Google Scholar etc. In addition, I also discuss the findings of my research with other scientist groups, local people, farmers, and staff of the forest department to get their point of view and suggestions.

IS: What do you think are some of the important current questions in social insect research, and what’s essential for future research?

Working with social insects is laborious work, time-consuming and often field-oriented, which is less appreciated by society and other research groups. However, social insects play a significant role in sustainable development. In the last decade, less importance has been given by funding agencies to conduct research on social insects due to the very limited number of scientists working on social insects, globally.

Also of notice, very few students express their interest to study and research social insects because of limited job opportunities. To overcome this, we should call for multiple research approaches and methods-based projects, meaning collaborative research with an allied subject should be conducted. We need to build-up teams/groups of scientists based on the different social insects they study, national-wise, state-wise, and if possible, area/district-wise. 

IS: What research questions generate the biggest debate in social insect research at the moment?

This depends on the situation and demand to nature, society, and evolution. Particularly the influence of termites in natural ecosystems is poorly explored when compared to other social insects like bees and wasp as well as other ecosystem engineers such as earthworms. Termites also play a big role in nature, society, and even for human beings. I think it is a debatable question why termites have been given moderate importance compared to other social insects.   Also, we should focus on the exploration of new aspects of social insects especially termites, their biodiversity, and comparative studies among other groups of insects. 

IS: What is the last book you read? Would you recommend it? Why or why not?

Currently, I am reading two books:

1) How Insects Work, An Illustrated Guide to the Wonders of Form and Function―from Antennae to Wings by Marianne Taylor (2020).

2) Extraordinary Insects: Weird Wonderful by Anne Sverdrup-Thygeson (2019)

IS: Outside of science, what are your favorite activities, hobbies, or sports?

Spending time with family and friends, exploring a new place, meditation, cooking, listening to music, reading, and cricket.

IS: How do you keep going when things get tough?

I talk to my family and friends, meditate, or spend time cooking and listening to music. Sometimes I also like to go near water bodies (river or sea; based on the condition) and relax. 

IS: If you were to go live on an uninhabited island and could only bring three things, what would you bring? Why?

Some study material as it will be good to study in this undisturbed area, some cooking stuff to try a new dish and some electronic safety device to communicate in an emergency and protect me.

IS: Who do you think has had the most considerable influence on your science career?

Three people play a significant role in my research career: my Ph.D. supervisor (Dr. S. Gajalakshmi), and my PDF mentors (Dr. Pascal Jouquet and Dr. E.V. Ramasamy), and of couse my family members. These are the four pillars that taught me different aspects of research and improved my research career. 

IS: What advice would you give to someone hoping to be a social insect researcher in the future?

People have wrong opinions about social insects, especially termites, which are totally misleading to society as well as young people. Whereas termites play a significant role in society as well as in the ecosystem. We just need to explore the special attributes of termites such as degradation on lignocellulosic waste, found in huge quantities. The handling of this waste is a big problem around the globe. However, termites can handle it in a very efficient way as they do it in the natural ecosystem. I think this aspect should be explored in future work.

Secondly, termites also play an incredible role in soil and nutrients dynamic, which is also not much appreciated. Termite mound soil has a higher nutrient value in comparison to the surrounding soil, which could be used as manure for agricultural fields to enhance the soil fertility, as proven by African researchers. This needs to receive more attention in the future. 

IS: What is your favorite place science has taken you?

Pondicherry University, Puducherry, The Indo-French Cell for water science (IFCW), Civil Engineering Department, Indian Institute of Science, Bangalore (IISC), India, and the Western Ghats region of Kerala (forest and water bodies). Such a nice experience to explore many beautiful places and learning a lot, which I never expected during my graduate and postgraduate education.