Ants Crossing

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I found this colony of migrating ants on my way to work. They’re abandoning an anthill that’s situated on a small patch of grass surrounded by pools of rainwater. They formed a bridge of dead ants interlocked with half-drowned ones to cross the puddle, probably an ocean to the ants. I imagine these worker ants, enamored by a chemical signal of sorts, “martyring” themselves so the rest of the colony can march on to drier earth.

This behavior is described in evolutionary literature as part of a complex of behaviors in eusocial species. Behaviorists suggest that ant colonies have an altruistic worker caste that forego reproduction in order for fertile ants to have better chances of survival. These sterile ants take care of the larvae and fight off predators and competing colonies, often sacrificing themselves in the process. E.O. Wilson’s book, Sociobiology, presents three traits common among eusocial species  (1971:398-399):

(1) individuals of the same species cooperate in caring for the young, (2) there is a reproductive division of labor, with more or less sterile individuals working on behalf of fecund nestmates, (3) and there is an overlap of at least two generations in life stages capable of contributing to colony labor, so that offspring assist parents during some period of their life.

Self-sacrifice appears counter-intuitive at the individual level (I mean, who would want to be one of those ants forming the bridge, right?). Sociobiologists argue that this altruistic behavior seems to be a consequence of haplodiploidy, the mode of sex determination among ants (i.e., males only have only one copy of each chromosome while females have two):

Working from the traditional axioms of population genetics, Hamilton first deduced the following principle that applies to any genotype: in order for an altruistic trait to evolve, the sacrifice of fitness by an individual must be compensated for by an increase in fitness in some group of relatives by a factor greater than the  reciprocal of the coefficient of relationship (r) to that group…the coefficient of relationship (also called the degree of relatedness) is the equivalent of the average fraction of genes shared by common descent; thus, in sisters r is 1/2; in half-sisters, 1/4; in first cousins, 1/8; and so on. The following example should make the relation intuitively clearer: if an individual sacrifices its life or is sterilized by some inherited trait, in order for that trait to be fixed in evolution it must cause the reproductive rate of sisters to be more than doubled, or that of half-sisters to be more than quadrupled, and so on. (Wilson 1971:415)

Female ants are more sisters than regular sisters.  The sterile worker ants share 75% of their genes with their sister queen, who does all the reproducing by herself. Inclusive fitness theorists (basic idea outlined in the quote above), believe that this peculiar genetics is responsible for the altruistic behavior in ants–a sterile female worker caste devoting all their lives in ensuring the queen’s reproduction. In addition, Dawid Nowak et al (2007) also observed that life expectancy influences the ants’ engaging in risky foraging behavior; the shorter the life expectancy (or older), the greater the self-sacrifice for the benefit of the colony.

I came back a few hours later to check on the ant bridge. This time, the water has receded. There was a thin line of dead ants left. I thought only a few died in the crossing of the “great” puddle. But when i looked closer, the worker ants, using their mandibles, were picking their dead up. I followed the marching ants and, about a couple of feet away, on a dry space between grasses is an inch-high pile of dead ants, likely sterile females and probably older.

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For a nice blog review on the debates surrounding the evolution of altruism, please click:

The Good Fight

References:

Division of labour among workers with different life expectancy in the ant Myrmica scabrinodis
Sociobiology: The New Synthesis, Twenty-Fifth Anniversary Edition

Anarchist Mangroves

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the fiddler crab concurs
that the mangrove is an anarchist,
perfect in its defiance
from that liminal place
between the land and the sea:
trunks bent close to the ground,
roots interlocked like arms in protest
in this creeping war against the tides.
when the sea appears to be winning,
a million middle fingers
shoots through mud,
growing leaves,
extending borders,
giving more life in time.

 

Egret by the Road

 

While taking an afternoon walk, a white egret stood by the road parallel to where I was. I inched closer, crept on the bushes, and aimed my camera at the bird.

ImageThe bird noticed me of course: its long neck extending above the grasses, eyeing every movement I made. A few seconds later, the egret flew away. The spread of its wings was a nice contrast to the pale that the overcast skies gave to the landscape.

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Feeding Whale Sharks: Much Ado About Butanding

PhotobucketCebu Daily News recently reported two injured whale sharks in the seas off a coastal barangay of Oslob, Cebu. One whale shark had a spear driven to its body and another got struck in the head by a motorboat’s propeller. The incident had drawn widespread condemnation from all sectors of Cebuano society. A local officer of the World Wildlife Fund laid the blame on the “domestication” of the whale sharks or butanding as the reason for the incident and thus called for the stopping of whale shark-feeding activities due to its effect on the species’ “natural hunting and feeding patterns.”

The risk that habituation presents is troubling. Once animals are habituated, they drop their guard and are more vulnerable to a wide range of human activities. According to Mark Orams (2002:285):

An animal has few cues about whether a human approaching it has good or bad intentions and, unfortunately, not all humans are wildlife lovers.

…(A)nimals that become accustomed to receiving food from people tend to frequent areas where there is a lot of human activity. These areas tend to present greater risks to animals that are not adapted to avoid such things as cars, boats and aeroplanes.

It is in a wild animal’s best interest therefore, for them to remain wary of people. Of course, when they are being regularly provisioned with food they lose this wariness, they become habituated to human contact and, as a result, they are at greater risk of injury from someone who wished to do them harm.

Some experts posit that dependence on human-sourced food reduces the chances of a species to survive in the wild. Species that are heavily dependent lose the skills needed in the search and pursuit of prey and may die if supplemental feeding is stopped. Although the literature on whale sharks is silent on this topic, I think that the volume of a whale shark’s food requirement is too high to be completely dependent on hand-feeding. For the whale sharks, people are alternative food sources–one among many in a whale shark’s array of foraging strategies. Similar to the fishes of the Great Barrier Reef and the dolphins frequenting Australian tourist spots,  the whale sharks might also have retained their foraging skills despite getting human-sourced food from tourists.

PhotobucketSo, should the municipality of Oslob continue with the practice of whale-shark feeding? The typical knee-jerk reaction is to implement a total ban and just let the animals be “wild and free.” Aside from the obvious challenges of enforcement, this would also set back the gains of many NGOs that encourage fishers to shift from exploitative fishing to sustainable wildlife tourism. Historically, southern Cebu was the seat of commercial fishing in the Visayas, renowned in the past for the destructive muroami fishing technique. It is therefore imperative that communities and fishers in Oslob reexamine their relationship with the sea and allow them to explore alternative connections with the marine fauna and flora.

The municipality of Oslob should also learn from the practices of institutions involved in endangered species conservation, where supplemental feeding is a cornerstone activity in population recovery strategies. If done properly, food provisioning could help increase a species’ reproductive success (i.e., although no specific studies have been conducted on supplemental feeding and its impact on whale shark population, i think it’s worth a try). The Philippine Tarsier Foundation, for example, conduct habitat enhancement activities to increase tarsier prey population. In Africa, “vulture restaurants” have been opened up in various sites to extend the chances of population recovery for critically-endangered birds (see TIME article). Perhaps, the propensity of tourists and tour guides to feed whale sharks can be redirected to boost breeding and reproduction albeit in a controlled and carefully-managed setting (i.e. sensitive to the dangers that habituation may pose to the animals).

People are part of the natural environment. We shape and influence the environment around us and thereby present challenges to other species. Every habitat, migration route, ecological niche bear a mark of humanity’s impact (e.g., from climate change to predatory fishing). We are the ‘facts of life’ that other species learn to negotiate and adapt. The problem with a total ban (i.e., “of leaving animals alone”) is the implicit assumption that we can separate ourselves from the lives of other species. We are part of every species’ reality and the primary driving force in their survival or extinction.

Also posted also in Anthropology Corner.

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Orams, Mark B.  Feeding wildlife as a tourism attraction: a review of issues and impacts in Tourism Management 23 (2002) 281-293.

Impressions on a Visit to Guanica

This blog article can also be accessed at my other blog site, Anthropology Corner.

PhotobucketThe southern end of Puerto Rico is a place one could easily associate with old Western films because of its crusty and brown rolling hills. The mighty central cordilleras, a rugged spine of verdant forest across the island, trap the moisture that should have been reserved for these parts, rendering the terrain dry and desert-like.

The 2-hour drive from San Juan to Guanica is a good trip for understanding the impact of the central cordilleras on the Puerto Rican natural environment. Starting from Salinas, the surrounding topography turns yellow and brown, different from the usual tropical green valleys we associate with islands around the equator. Instead of trees dominating the landscape, what you see are grasses, shrubs, short scraggly trees, and cacti while a flock of migratory turkey vultures hovers above.

PhotobucketThe situation of being at the wrong end of the central cordilleras (with seasonal rainfall averaging only 860 mm annually) does not stop life from blossoming at this southwestern part of Puerto Rico. The unique topology and microclimatic conditions created a biome that has been described as the “best preserved and best example of a tropical dry forest in the Caribbean.” This United Nations Biosphere Reserve is home to nine of the fourteen endemic bird species of the island and a host of other flora and fauna.

This 4000 ha. forest reserve however is sandwiched in tourist, agricultural, and urban development zones. The main road leading to the Guanica State Forest shows a landscape bearing its story of human occupation. A cursory look by the roadside would show that certain portions of the land are devoted to cattle and horse grazing. The plains are turned into fields of banana, papaya, and vegetables–the primary cash crops of Puerto Rico. Back in the day, historians recorded that the southern area also had a thriving sugar industry like the rest of the island but was abandoned when the world prices of sugar dropped to record lows (Guanica ending it in 1981). Vestiges of that sugar culture can still be gleaned from the artisanal production of guarapo, a sugarcane juice drink, and ron cana, a toxic sugarcane rum that burns your insides.

PhotobucketThe seaward edge of the Guanica dry forest is a winding road that threads the series of hotels and beach spots along the coasts. Sightseers and tourists go to this area primarily because of the beach and Gilligan’s Island, an islet just across the forest. From the road, footpaths go deep into the forest reserve where hikers climb the rocky hills and explore the remarkable flora and fauna. Occasionally, a Santeria shrine of a saint could be found bearing offerings of fruits and flowers.

I don’t know how much of an impact human activities contributed to the Guanica Dry Forest. I tried searching through the literature and found that studies along this line have been wanting. What I saw instead was a comprehensive study of the influence of hurricane winds on the dry forest cycles. Apparently, dry forests are resilient enough to confront winds as strong as 152 knots. But droves of people? Who knows.

Thinking hermit crabs today

What is it with hermit crab these days? I find them by the mangroves, the sandy beach, decaying trees, and across various spaces on this little island. I literally trip over them and sometimes hear a crunch under my boots whenever I search for my monkeys. Many of them prefer to hide under the shade to escape the glare of the sun and, if you lift a decaying log, there they are in clumps, one over the other, packed like cars on a junkyard.

Nothing is more poetic than the union of an abandoned ivory shell and a crustacean in need of a home.  The hermit crab, devoid of its shell, has a belly so soft that a little squeeze can spread its guts out. It looks ugly and walks like a drunk pirate when left out “naked” in the open. Once it meets the shell of the proper size and condition, it wriggles itself in, making the shell a part of its anatomy until the crab outgrows it and has to find another shell again. The shell is the toughest armor in the crustacean world; after all, if the previous owner was safe in it, so will the current occupant be.

The shell is the central axis of the hermit crab’s defensive repertoire. A little movement and they retreat to their shells, shutting the entrance with their claws, and never to come out unless the danger has gone. Too slow to run because of the weight of their shell, they embrace themselves tight that in the process they close off the world outside. They’d rather fall from a higher ground and come down hard to the beach floor than fight off intruders. Their claws, while capable of slicing a finger, are designed more to be impenetrable doors than weapons.

If you wish to elicit a response from the hermit crabs behind their shell fortresses, try knocking on the bigger ones, especially those that have grown bigger than your fist. Every knock is answered back with a complaint. They scratch the insides of their shell, emitting a sound like a cross between the grinding of a pencil sharpener and the turning of a rusty wheel sprocket. When everything is still, the hermit crab slowly emerges from its hiding place, stretching its spindly legs, one after another. The antennas poke out of the shell like copper wires and then the rest of the head emerges. The eyes, matchstick black, scan the surrounding and in a rush the hermit crab lumbers to the nearest thicket. Once it feels safe, the crab curls back up again inside its shell.

Back home, we call the hermit crabs umang. They are way smaller than the ones on the island. Children in fishing villages collect them and put the umang inside a tin can. Sometimes, they would play with the critters: two hermit crabs are held face-to-face by the back of their shells to make them fight. As expected, they don’t fight. They didn’t evolve much for fighting. The umang merely push each other out of the way and then pinch the skin of the holders’ finger to escape. I think what excites the child’s curiosity is not so much the “fight” but the sword-like movement of the legs, almost like a samurai’s katana in hypnotic movement. When they fall from the child’s grip, the umang are picked up again for another round of “fighting.” This will only stop when the children smash the shell with just enough force,  breaking the shell but leaving the hermit crab exposed. Then, the tender and soft belly is separated from the rest of the body. For these child-fishers, hermit crabs are fish baits.

So if I ask again what is it with the hermit crabs today? Tell me it wasn’t smashed for fish bait this time. Tell me that I am squishing them under my boots.