Posts Tagged ‘predators’

Nature Ramble

How the threat to lions, leopards and wolves endangers us all

Though fearsome killers, big carnivores are also a precious resource, as their feeding habits keep many delicate ecosystems in balance. But too many predators are now facing extinction

Lions kill a buffalo in Kenya’s Masai Mara National Reserve. Photograph: Jonathan & Angela Scott/Getty Images/AWL Images RM

They are the planet’s most prolific killers – and also some of nature’s most effective protectors. This is the stark conclusion of an international report that argues that lions, wolves, pumas, lynxes and other major carnivores play key roles in keeping ecosystems in balance. It also warns that the current depletion of numbers of major predators threatens to cause serious ecological problems across the globe.

The paper, written by a group of 14 leading ecologists and biologists from the US, Europe and Australia and published in the journal Science, calls for the establishment of an international initiative to conserve large carnivores and help them to coexist with humans. Failure to protect our top predators could soon have devastating consequences, they warn.

“Globally, we are losing our large carnivores,” said William Ripple, the report’s lead author. “Many of them are endangered and their ranges are collapsing. Many are at risk of extinction, either locally or globally. And, ironically, they are vanishing just as we are learning to appreciate their important ecological effects.”

The report has been produced, in part, to show that the classic vision of a large predator, such as a lion or a wolf, being an agent of harm to wildlife and a cause of widespread depletion of animal stocks is misguided. Careful analysis of predators’ food chains reveals a very different picture. “In fact, the myriad social and economic effects [of large carnivores] include many benefits,” it states.

Ripple, a professor at Oregon State University’s department of forest ecosystems and society, and his colleague Robert Beschta, have documented the impact of wolves in Yellowstone and other national parks in North America. When wolf numbers have been reduced, usually by hunters, this has led to an increase in numbers of herbivores, in particular the elk.

Elks browse on trees such as aspen, willow, cottonwood, and various berry-producing shrubs, and the more elks there are, the more browsing damage is done to these trees. The knock-on effect is striking, says the report.

“Local bird populations go down because they have fewer berries to eat,” added Ripple. “The same is true of bears, which also eat berries. Beaver populations are also affected. They have less plant life to eat and less wood for making their dams.

“For good measure, the roots of the willow and other shrubs help to hold the soil of river banks together, so they do not get washed away. This does happen, however, when you have no wolves, lots of elks and, therefore, poor levels of vegetation. So you can see that the wolf – which sits at the top of the food chain in midwest America – has an impact that goes right down to having an effect on the shapes of streams.”

Yet wolves were once considered to be such a menace that they were exterminated inside Yellowstone national park in 1926. The park’s ecology slowly transformed with their absence until, in 1995, they were reintroduced.

“Very quickly, the park’s ecosystems returned to normal,” said Ripple. “I was impressed with how resilient it proved.”

Another example of the ecological importance of large carnivores is provided by lions and leopards. Both animals prey on olive baboons in Africa, and as numbers of these key predators have declined, numbers of olive baboons have increased. The population of lions in particular has been so reduced that it now only covers 17% of its historical range, while numbers of olive baboons have risen in direct proportion.

The consequence of this increase has been significant, say the authors. Olive baboons are omnivores and eat small primates and deer. When olive baboon numbers rise, populations of local monkeys and deer plummet. There is also an effect on human populations.

“Baboons pose the greatest threat to livestock and crops in sub-Saharan Africa, and they use many of the same sources of animal protein and plant foods as humans,” states the Science paper. “In some areas, baboon raids in agricultural fields require families to keep children out of school so they can help guard planted crops.”

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Nature Ramble

We all know seahorses exist. They are cutesy vertical swimmers, but very few people have seen them, or know much about them.

Here’s BBC News story:

Seahorses stalk their prey by stealth

Seahorse, or sea monster? You can watch the hunter stalking its victim (on the BBC Link)

Seahorses may appear slow and awkward but they are ferocious and ingenious predators, according to a new study.

The beautiful creatures are famously bad swimmers, but they have a secret weapon to sneak up on their prey.

Their peculiar snouts are shaped to create very few ripples in the water, effectively cloaking them as they creep up and pounce on tiny crustaceans.

To their victims, seahorses are more like sea monsters, say scientists from the University of Texas at Austin.

“The seahorse is one the slowest swimming fish we know of, but it’s able to capture prey that swim at incredible speeds,” said Brad Gemmell, author of the study in Nature Communications.

The prey, in this case, are copepods – extremely small crustaceans that are a favoured meal of seahorses, pipefish and sea dragons (Syngnathidae).

When copepods detect waves from predators, they jolt away at speeds of more than 500 body lengths per second – the equivalent of a 6-foot human swimming at 2,000 mph.

Deadly strike

“Seahorses can overcome one of the most talented escape artists in the aquatic world,” said Dr Gemmell.

“In calm conditions, they catch their intended prey 90% of the time. That’s extremely high, and we wanted to know why.”

The dwarf seahorse may look delicate, but its snout is a lethal weapon

Seahorses dine by a method known as pivot feeding. Their arched necks act as a spring – allowing them to rapidly rotate their heads and suck their prey in.

But this suction only works at short distances. The effective strike range for seahorses is about 1mm. And a strike happens in less than 1 millisecond.

Until now, it was a mystery how such apparently docile creatures managed to get close enough to their prey without being spotted.

To find out, Dr Gemmell and his colleagues studied the dwarf seahorse, Hippocampus zosterae, which is native to the Bahamas and the US.

They filmed the movement of water around the fish in 3D using holography – a technique where a microscope is fitted with a laser and a high-speed digital camera.

They found that the seahorse’s snout is shaped to minimise the disturbance of water in front of its mouth before it strikes.

Above and in front of its nostrils is a “no wake zone” and it angles its head precisely to attack its prey.

Other small fish with blunter heads, such as the three-spine stickleback, have no such advantage, the researchers found.

“It’s like an arms race between predator and prey, and the seahorse has developed a good method for getting close enough so that their striking distance is very short,” said Dr Gemmell.

“People don’t often think of seahorses as amazing predators, but they really are.”

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Dwarf Seahorse, Hippocampus zosterae

Dwarf Seahorse, Hippocampus zosterae

 

Make you Fink on Friday

Street lights ‘changing ecology on the ground’

The study could have big implications for a shifting of the ecology in urban and suburban areas

The presence of street lights substantially changes the ecology of ground-dwelling invertebrates and insects, research suggests.

Scientists trapped nearly 1,200 of the animals in areas under and between street lights in Helston in Cornwall.

They report in Biology Letters that invertebrate predators and scavengers were more common near the lights, even during the day.

That suggests street lights influence ecology more than previously thought.

Much work in recent years has gone into addressing the effects that street lights can have on local, transient populations of bugs – particularly those that can fly and have significant ranges of exploration.

But the effects of street lights on the vast communities of invertebrates on the ground remained unaddressed.

Source: BBC News Read more

Opinion:

There, just another example of man’s guilt at changing the nature of things.

Everything man does, has an adverse effect on the environment.

Bugs under street light photo time-lapse photography

Now, on the surface, we may not think that altering the habitats of ‘bugs’ is that important. But what if a particular ‘bug’ was required to prey on another particular ‘bug’ and one was and the other wasn’t attracted to light. Then the ‘bug’ that was controlled is now free of predators to swarm and multiply so that it becomes a noxious pest, possibly to the detriment of mankind.

There exist also possibilities of street lights being the cause of extinction. Fireflies, for example, prefer street lights to sex, because the street lights are brighter than the signal light for sex from their own species.

Invasive Species

Battling the brown tree snake in Guam

In the dense tropical forest, a slither of movement can just be made out in the glow of our head torches.

A snake is entwined in the undergrowth. It is about 1m long, mostly dull brown but with a vivid yellow underbelly.

We are face to face with Guam’s “nemesis”: the brown tree snake. And the forests here are dripping with them.

The US territory, in the western Pacific, is only 50km (30 miles) long and 10km wide, but it is packed with two million snakes.

This reptile arrived here only 60 years ago but has rapidly become one of the most successful invasive species ever.

Unhealthy appetite

Wildlife biologist James Stanford, from the US Geological Survey, says: “Our belief is that they came at the end of World War II.

“We’ve looked at their genetics and they are all extremely closely related, and it appears they came from the Island of Manus in Papua New Guinea.”

He explains that military equipment used by the US in Papua New Guinea while the war raged in the Pacific was eventually sent back to Guam to be processed. A snake probably crept on to a ship or a plane destined for the island.

“And from that handful, or maybe even one already impregnated female, we now have a population that is unbelievable in scale,” he says.

The snakes, which are mildly venomous, have caused many problems. They get everywhere, and people have even woken up with them in their beds.

The island’s power system is regularly shorted out by snakes crawling on the lines. It is so frequent the locals now call power cuts “brown outs”.

But the biggest impact has been on the wildlife – it has been decimated. The forests here are eerily quiet. Now the only place where the Guam’s native birds, such as the koko, can be seen on the island are in cages in a captive breeding centre.

“The brown tree snake has had a devastating impact. Ten out of 12 native forest bird species disappeared in 30 years,” says Cheryl Calaustro from Guam’s Department of Agriculture.

“The birds here evolved without predators. They were quite naive. And when the snake arrived on Guam it ate eggs, juveniles, adults. Whole generations disappeared.”

Source: BBC News Read more

Comment:

Another example, although inadvertant in this case, of how man’s carelessness damages the natural balance.

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