Monday, June 18, 2018

Animals are getting more nocturnal to avoid humans

Animals that are millions of years old being diurnal are moving into the night. Whether big or small, forest or savanna, predators or prey, species from all over the planet are transferring the bulk of their activity to the night time. A large study points to the expansive human presence as the cause of changes that can disrupt the dynamics of entire ecosystems.

The impact of humans on wildlife has many edges. The most obvious is the contraction of the space available to animals as the human race has been expanding throughout the planet. In addition, these natural spaces are increasingly reduced and quartered and their quality is reduced with each new infrastructure that surrounds them. One of the consequences of all this is that animals move less and less in areas with human presence and take refuge in increasingly smaller areas. But there is another way to hide from humans: leave when they go to bed.

A group of researchers from the United States has verified the global nature of this translation of animal life to the hours in which the great diurnal predator rests. Compiling the results of dozens of studies on the movements of some 60 species of mammals from five continents, scientists have found that, where there is a human disturbance, mammals are, on average, 1.36 times more nocturnal. This means that an animal that, without disturbances, equally distributes its activities between day and night, would increase its nocturnal activity up to 68%.

"There is evidence to suggest that animals everywhere are adjusting their daily activity patterns to avoid humans over time, as it is increasingly difficult to avoid them in space," says the researcher at the University of California at Berkeley. (USA) and principal author of the study, Kaitlyn Gaynor. "As people are more active by day, animals are moving into the night," he adds. This transfer occurs whether it is herbivores or large carnivores such as the tiger. The pattern is repeated both in smaller mammals such as the opossum, and in those weighing more than 3,500 kilograms, such as the African elephant.

The most striking aspect of this review, published in the journal Science, may be that animals are becoming more nocturnal regardless of the level of danger that humans pose. "We expected to find a tendency to increase nocturnality in the vicinity of humans, but We have been surprised by the consistency of the results. The animals respond to all types of human disturbance, regardless of whether it really poses a direct threat, "he adds.

Gaynor's work is based on dozens of studies that used various tracking techniques (beacons, collars with radio transmitters, GPS, phototraps or direct observation) of the movements of the animals before a range of human presences, from hikers to hunters, going through fields or roads. One of those studies tracked a species as opportunistic as the fox for lands of Castilla-La Mancha in a series of minor environments (Cabañeros national park) to greater human presence (around Ciudad Real).

"Although it is a twilight animal, the more human disturbance, the fox tended to reduce its diurnal activity," says the biologist at the University of Malaga and co-author of that study, Francisco Díaz. For the most nocturnal foxes, there was a temporary mismatch with their main prey, the rabbit, eminently diurnal. Fortunately for them, the foxes are among the most adaptive animals. "But there are other species with millions of years of adaptation to daytime behavior that are not so plastic," Díaz recalls.

The consequences of this transfer to the night of so many species are still uncertain. In principle, it would seem that the abandonment of the day in favor of humans would facilitate the coexistence between humans and animals. But such a widespread and rapid change of patterns of activity molded over millennia can alter an entire ecosystem. "In the case of predators not adapted to hunting at night, there could be an increase in the population of the ungulates that were their prey, which would affect the availability of vegetation cover, producing a cascading effect," says the Researcher at Radboud University, Niimega (The Netherlands), Ana Benítez.

For the Spanish ecologist, who has also investigated the different human impacts on animal life, the most relevant of this research is that it confirms a hypothesis raised in the 60s by the biologist Fritz R. Walther: "Animals respond equally to humans , they always see us as predators, "he says. This leads to the question whether the impact of a hunter can be the same as that of a nature-loving hiker. For Gaynor, his research "suggests that our mere presence is enough to interfere with natural behavior patterns".

Thursday, July 12, 2007

Brightly Colored Birds More Affected By Chernobyl

On ScienceDaily today, a really fascinating report on how the Chernobyl meltdown has affected some bird species more than others. They studied 57 species, and found that those that have had the most drastic declines since the disaster fall into four groups:

1. Species that depend upon dietary carotenoids for their red, yellow, or orange plumage (orioles, blackbirds, blue tits, for example).
2. Species with relatively large eggs.
3. Species that migrate.
4. Species with wide dispersal patterns.

Apparently all of those groups have lifestyles that place a high demand on antioxidants (for plumage coloration, flight energetics, etc). The study suggests that high levels of radiation have a disproportionately negative impact on species that require lots of antioxidant compounds. Radiation levels in a normal (ie not post-meltdown) environment vary due to natural things like differences in isotopes between different geological features, and the researchers suggest that these new discoveries can be used to make predictions about species success in places where radiation levels can be quantified.

It is important to realize, from the data in their report, that some of the species studied fall into more than one of the high-risk groups: for example, orioles depend on carotenoids for their yellow plumage (see image above), and also migrate long distances.

Also, another thing I gathered from the report that I thought warranted a note: bird species that are taxonomically close might not be impacted to the same degree as less-related species with similar lifestyles (meaning, you can't necessarily predict the impact on a species by looking at stats on a sister species). For example, in the family Paridae, blue tits, which are highly dependent on carotenoids, have faced much sharper declines than coal tits.

I've always been fascinated with the Chernobyl meltdown (it's one of the landmark events in the year I was born, btw) and its impacts on the local wildlife. Despite my unabashed mammal and dino bias as far as interests go, the radiation-eating fungus recently discovered there is still definitely my favorite science story of 2007 (see my blog post on it here). One thing that is both interesting and sad is that some reports have shown that wildlife has actually benefited, in some ways, from the catastrophe, since human activities in the area have effectively ceased.

Wednesday, July 11, 2007

Quotes of the day

"How is it that hardly any major religion has looked at science and concluded, 'this is better than we thought!' The Universe is much bigger than our prophets said, grander, more subtle, more elegant'? Instead they say, 'No, no, no! My god is a little god, and I want him to stay that way.' A religion, old or new, that stressed the magnificence of the Universe as revealed by modern science might be able to draw forth reserves of reverence and awe hardly tapped by the conventional faiths."
Carl Sagan in The Pale Blue Dot

"The distinguished embryologist Lewis Wolpert once admitted that science is occasionally arrogant, and he went on to remark, mildly, that science has a certain amount to be arrogant about."
Richard Dawkins in Unweaving the Rainbow

Monday, July 9, 2007

Worm-like jellyfish

There is a really fascinating article on Science Daily today about Buddenbrockia, a small organism previously that has long been thought to be a nematode worm, but now known to be most closely related to anemones and jellyfish. It has no gut, mouth, brain, or nerve cord, and although it was long thought to be a type of nematode, it has a very different body plan (the main distinction: Buddenbrockia is symmetrical).

Researchers from the University of Oxford compared 50 genes with a variety of organisms to determine where this enigmatic species fits into the animal kingdom.

There are practical implications for this as well: apparently Buddenbrockia is closely related to a parasite that causes trouble for salmon farms (I don't have time to go into my issues with salmon farming the first place, though...). Current and future studies of it will hoepfully shed light on how to conquer the parasite, although I think that the taxonomic revelations are pretty cool all on their own.

(Photo credit: University of Oxford)

Sunday, July 8, 2007

Could you solve it?

Scenario: You are shown a tall cylinder with a tasty nut in the bottom. How do you go about getting it out, assuming the cylinder is too tall and narrow for you to reach the bottom, and that it is fused to a tabletop (you can't dump it out)?

Could you create a strategy for getting the nut? Orangutans in one study showed amazing problem-solving skills to obtain the nut: they took mouthfuls of drinking water and spat into the cylinder, to make the nut float within finger-grasping range.

The five orangutans tested needed an average of nine minutes to realize that they could float a peanut to the top of the container, you can see an example here:

Pretty amazing, I think! Orangs are infamous for using tools and escaping enclosures in captivity (read about the legendary escapades of Fu Manchu here), which is interesting because in the wild they have not been observed to use tools to the same degree as other apes, or to captive members of their own species.

If I could pick one primate to study it would definitely be the orangutan, there is so much about the species that is unique from the other great apes. They are so imperiled right now, though, and often from places people wouldn't expect, like efforts to promote biofuels instead of fossil fuels. You can learn more about orangutan conservation efforts here, the statistics are very disturbing.

Thursday, June 28, 2007

Van Roosmalen sentenced to 14 years in jail

Earlier this month I did a post on Marc van Roosmalen, a zoologist that has discovered an unbelievable number of new vertebrates during his career. I came across this news story today and was shocked, apparently he's been sentenced to 14 years in jail for "theft and biopiracy", as a result of failing to apply for permission to create a monkey refuge at his home. The linked article speculates that this happened because his efforts toward promoting conservation have made him a nuisance to Brazilian authorities.

According to the blog, if an application like this is not rejected within 45 days it is generally assumed to have been accepted, which is what van Roosmalen apparently did without realizing it had been rejected...although he has been accused of never filing it in the first place. I think it sounds like a very suspicious situation, pretty convenient for the officials to lose the document and then have a reason to arrest the scientist. He is appealing the decision, hopefully it will be overturned, he is 60 years old and a 14 year sentence would end his career and all of the conservation efforts he is making.

Tuesday, June 26, 2007

Giant penguins in Peru!

Fascinating press release today, this week's Proceedings of the National Academy of Sciences, has a paper describing two new species of fossil penguins, found in the Atacama Desert (Peru).

One species (Icadyptes salasi) dates from 36 mya, and stood 4.5 feet tall. the second species (Perudyptes devriesi ) is older, from 46 mya, and stood about 3 feet tall, roughly the same as modern King Penguins. There are still penguins in South America today Spheniscus humbolti), but the extant species is only about 2 feet tall.

This find is interesting because it pushes the appearance of penguins in this region back by about 30 million years. It is also fascinating because such large birds were present in a relatively warm climate, apparently early penguins were not the cold-specialized birds that we see around us today.

This find looks like it could rewrite the known history of the Spheniscids, the new specimens definitely hold promise to reveal much more about penguin evolution than what was previously known.