Why is Megabiota conservation’s poster child?

The health of all life on earth has now been shown to hang upon a “small” group; if the few giants of the planet are in trouble, it might mean giant trouble for the rest of the planet, research shows.

elephant

Photo source: Anthropocene magazine

One of the most prominent effects of the present age of ever-increasing significant human impact (the Anthropocene) is the extinction and reduction of the earth’s largest plants and animals (megabiota): the giants of the planet. Since the populations of these organisms are limited by a combination of natural and human-induced factors, they are the most susceptible to destruction during such rapid change as we see in these times.

Debate is rife on the value of large organisms like elephants, whales, and huge trees (such as redwoods and sequoias), for conservation planning and as good indicators of conservation efficiency. This is especially so considering their common use as symbols for conservation campaigns. The big question is this: is it merely about their charisma and the admiration their size inspires? Or is it something more?

A study published in Nature in February this year demonstrated that large organisms are more prone to extinction with increasing human activities. It also showed that the reduction in their numbers and their eventual extinction is, and will be detrimental for the complex workings of biological systems on earth i.e. ecosystem functioning.

Using simulations and forecasting methods, several international authors compared what the physical world was like before humans started destroying earth’s giants through the destruction of their habitats; what it is now, and what it will be in the event of their extinction. The study found out that the loss of large animals will reduce the total amount of wild animal biomass on the planet by about two-fifths (44%). Also, in the absence of large organisms, soil fertility will reduce by 92%.

The study showed that not only will the removal of large organisms negatively affect life on earth, but the effects will also be bigger than is expected i.e. multiplicative. This is because the largest organisms are the largest reservoirs of nutrients and the mobile groups (animals) additionally transport these nutrients through their movements. The loss of these giants will have implications for nutrient cycling; and thus, biodiversity, ecosystem function, and climate change mitigation.

The lead author, Brian Enquist, professor of ecology and evolutionary biology from the University of Arizona, gave an analogy, “The largest banks and corporations in the economy are the most productive and have the most impact on the economy, so when those large banks failed… we had to prop them up economically, or they would have had a disproportionate negative impact on economy. It’s a similar principle with large plants and animals across ecosystems.”

Dr. George Wittemyer, a Colorado State University scientist who was not involved with the study, considered the study to be interesting, and a call to pay attention because as he said, ”the scale of impact is really striking”. He also observed that “The {study’s} main take-home message is that the amount of perturbation on the system {due to megafauna removal} could be substantial and disruptive”

This study suggests to us that the giants of the planet have more value than their size-associated charisma; the size of their importance within the ecosystem is as gargantuan as they are.

“Protecting big, charismatic species does have an umbrella effect to protect the wider ecosystem”, Prof. Enquist said.

Mei Xiang

Photo source: Smithsonian zoo

What is not common about Common Bulbuls in Nigeria

 

When you watch birds in Nigeria, some birds become boring to you after a while. It’s because they are so common! And birders particularly enjoy identifying a new, and preferably rare, bird species.

According to the Bergmann’s rule, individual animals should be bigger in cold environments than those of the same species living in a hotter environment. Studies have found this rule to apply on a global scale across latitudinal gradients; with lower temperatures in higher latitudes, i.e. regions farthest from the equator. The Bergmann’s rule has now been observed to apply locally, in a bird species within Nigeria, in the same latitude. A 2018 study in the Journal of Ornithology found that Bergmann’s rule is evident among Nigeria’s Common Bulbul.

Photo credit: ebird.org

 

The Common Bulbul (Pycnonotus barbatus), which is common within Africa as its name implies, was trapped from southern Nigeria to northern Nigeria along an environmental gradient, with hotter and drier conditions towards the north. This study was done by scientists, some affiliated with the A.P. Leventis Ornithological Research Institute in Jos, Nigeria. These scientists captured five hundred and thirty-eight (538) individual Common Bulbuls from 22 sites within Nigeria. Body mass, wing length, and other measures of body size were measured for each individual. They tested the data to see if the body size (determined by surface area to mass ratio) of the Common Bulbuls would depend on how dry and hot their environment was.

The lead author, Dr. Chima Nwaogu said, “By using a species like the Common Bulbul which is everywhere, since the issue of variation in phylogeny {i.e. differences between animal groups} has been taken care of, we can focus on the effect of variation in environmental conditions on that species”

Nwaogu had observed differences in bird sizes while he trapped Common Bulbuls in different locations for his Ph.D. study. Having read about the Bergmann’s rule, he decided to test it on the size data of the birds. To his surprise, he found the birds to be smaller in the northern part of the country where it is hot and dry, and bigger in the south where it is cooler and wetter. And this size difference was predicted by temperature and rainfall variables. Thus, the Common Bulbul was found to obey the Bergmann’s rule, relative to temperature differences, within similar latitudes.

Although this phenomenon (Bergmann’s rule) is thought to be a way that animals regulate the impacts of temperature on their bodies, Nwaogu believes that the differences in Common Bulbuls size across these environmental conditions may also show the effects of climate change. This may be so if the birds are observed to change in size over time. He suggests that continued monitoring of Common Bulbul sizes in Nigeria, could help us determine how the environment is changing: e.g. if a particular location is getting drier or hotter, we might observe that the Bulbuls would start getting smaller.

Dr. Volker Salewski, a scientist with NABU, who was not involved with the study, was unsurprised by the findings of the study. He thinks that while this particular study cannot give any evidence for climate change, “it highlights {the fact} that birds adjust their morphology to the environment they live in”. “The value of studies such as this”, said Salewski, “is that it can be used to draw inferences about the consequences of climate change… The question is whether {the birds} will be able to change fast enough to cope with the changes we are observing now”

As a species that may allow us to peek into a natural evolutionary experiment as climate change unfolds, perhaps the Common Bulbul is not so common after all.

Owls and omens (What’s the deal with owls?)

Once, when we were much younger, my sister told me of a bird her friend’s family had seen in their house.

“How can a bird turn its head 360°?!” she had asked in disbelief. Actually, the bird could only turn its head 270°.

confused owl
Photo Credit: Oladele 

But either way, such non-human head-turning was a bad omen. Therefore, the bird was killed.

I once heard my neighbour ask, after killing an owl which was resting in the daytime, “Why is it that it is only at night that this bird is active, if it is not a witchcraft bird?”

Owls are ill-fated creatures, especially in places (such as Nigeria) in which every mystery is attributed to the supernatural, and mystery almost always translates to danger. Therefore, we need to shed the light of knowledge and demystify these poor (and sorely persecuted) creatures because in the real sense, and based on scientific knowledge, owls are fascinating creatures.

Owls are animals that are specially adapted, with their very sensitive eyes and ears, and silent flight and camouflage, not just for nightlife, but for efficient predation in the dark. This is one of most unique and fascinating aspects of their life history. And it (their nocturnal habit) is perhaps, one of the scariest things about owls to Nigerians. The nocturnal adaptation of owls also helps them avoid competition from the many bird species which hunt in the daytime. Therefore, they are the perfect match for our pesky nocturnal pests which are also active at night.

Barn owl swooping - Tyto alba
Photo credit: Andy Harmer

Like most other predators, owls regulate the populations of the animals they feed on. What this means is; if we are good neighbours to the owls around us, we wouldn’t need to use so much rodenticides (which put our animal scavengers at risk anyway). Owls are an effective means of natural pest control, and feed on urban pest species such as rats and mice, which are prone to growth explosions.

In urban areas, owls come closer to us than they ever did when we still lived in villages (surrounded by natural environment such as forests). Often, some of us hear the barn owl snoring in our roofs.  This is because owls are taking advantage of the tall structures and abundant food in urban areas. They can build safe nests in tall structures and raise many babies with the abundance of food (in form of the pests that come to feed on our overflowing food stores and waste). In the natural environment, food could be really scarce; this is why they readily move in close proximity to humans.

This is not to cast an image of owls wearing halos, and dutifully carrying out pest control, and not making a nuisance of themselves.

Like any wild animal, an owl will defend itself and its family if it feels attacked, cornered or threatened. It will probably snore noisily while it sleeps in your roof (especially if it is a barn owl), and it might poo or regurgitate pellets on your newly painted walls. But we (humans) are not perfect either. If you are honest, your neighbour (or roommate, or whoever lives the closest to you) can point out something about you that really annoys them. So, we can always find a way to tolerate another annoying but helpful neighbour, can’t we?

Although owls are not angels, but are in fact, about as wild as any other brute beast, they also deserve to live and play their part in this beautiful home (earth’s cities/towns/forests) which we share with them, because owls are an important and fascinating aspect of the terrestrial ecosystem (the web of life on land).

If you live in an urban area in Nigeria, you are more likely to have the barn owl as your neighbour. If you live in a rural area, there are many other species. So, the next time you see (or hear) an owl or owls, by all means think of an omen. But when you think of an omen, think of a good omen: pest control, efficient pest control.

Moving Targets: a tale of survival

An urban wildlife tale: predation in the city

The drama took only a few seconds to unfold.

And here’s how it happened.

About 15 feral pigeons (Columba livia domestica) are feeding tamely beside the road.

Photo credit: commons.wikimedia.org

Suddenly, a Yellow-billed Kite (Milvus migrans) glides out of nowhere, into sight, in all its broad-winged, fork-tailed majesty.

Photo credit: Wilkinsonsworld.com

The pigeons know the kite hasn’t come to show off its beautiful feathers or flying skills. Without losing any time, they take off to safety in as many different directions as there are pigeons.

The kite, unfazed, promptly fixes on one of the pigeons in hot pursuit.

It just happened that I was standing on the opposite side of the road from the action, with a companion, on that hot Sunday afternoon, watching the story play out (it was like Nat Geo Wild, live!)

As I stood there, watching one of my favourite topics in behavioural ecology (predation avoidance) play out before me, and thoroughly enjoying myself, I was asked by my companion, “but why did the kite focus on that single bird?”

Good question.

The answer: to increase its chances of securing a meal.

Animals which are targeted as prey develop behaviours by which they avoid being another animal’s ‘breakfast’. We call this, in animal ecology, predation-avoidance behaviour. One such behaviour is seen in the formation of groups, to enable individuals take advantage of the safety in numbers.

In addition to group-forming, birds (and some other animals eg. fish) also evade predators with what is called the “confusion effect”. When a predator shows up, all the birds in the group take off at the same time, giving the predator several moving targets. This leads to confusion, and reduces the chances of the predator catching any one individual.

Photo credit: PxHere.com

Clever, isn’t it?

However, if the predator is smart enough to know to single out a target (like the kite in my story); it increases its chances of successfully making a kill, and thus securing ‘dinner’.

Unfortunately (for the prey), the greater the difficulties involved in obtaining food (which is so essential for survival), the wiser predators become. And in turn, the wiser (and faster) the prey have to be because their lives are at stake.

Anyhow, at the end of the chase in the story I just related, the kite lost a meal, and the pigeon gained its life for a few more minutes. Or perhaps hours, days, or even years….you never know.

Thanks to the companion whose question inspired this article, and to the friend who gave me, on the same plate, a deadline to put up a blog post, and the threat of a bad name, namely: reneger (okay, I exaggerate).