Were the dinosaurs laid low by insects?

A huge meteorite around 65m years ago is believed to have caused massive global climate change that led to the extinction of the dinosaurs. However, according to a new theory they may have in fact been pushed to extinction by insects .

According to a new hypothesis by entomologists George and Roberta Poinar the later part of the dinosaurs' era saw an explosion in insect diversity and in the process dealt a double whammy to the reptiles - they spread disease and contributed to a transformation of vegetation which the plant-eating reptiles failed to adapt to.

"We can't say for certain that insects are the smoking gun, but we believe they were an extremely significant force in the decline of the dinosaurs," said Poinar. "Our research with amber shows that there were evolving, disease-carrying vectors in the Cretaceous period, and that at least some of the pathogens they carried infected reptiles. This clearly fills in some gaps regarding dinosaur extinctions."

In the gut of one biting insect preserved in amber - fossilised tree sap - from that era, the team has found the pathogen that causes the parasitic disease leishmaniasis, and in another they found a type of malaria parasite that infects birds and lizards. By inspecting fossilised dinosaur faeces, the team also found parasitic microbes that are carried by insects.

In addition to spreading disease, insects were busy pollinating flowering plants. These gradually took over from seed ferns, cycads and gingkoes. If herbivorous dinosaurs could not adapt to this new diet they would have gone hungry.

Poinar believes that the most popular theory for the dinosaurs' demise - that a meteorite impact changed the global climate - falls short because the extinction took too long. "Other geologic and catastrophic events certainly played a role. But by themselves, such events do not explain a process that in reality took a very, very long time, perhaps millions of years. Insects and diseases do provide that explanation."

I have no idea whatsoever if Poinar’s hypothesis holds water but it does sound intriguing

Hope for the baiji?

There are reports in the Chinese media of a sighting of the Baiji, the Yangtze River or White Flag Dolphin. The dolphin was declared to be functionally extinct by scientists just three weeks ago .

According to the Xinhua News Agency a “big white animal” was spotted and filmed by a resident of east China's Anhui Province on 19 August. The animal in the footage was confirmed to be a baiji by the Institute of Hydrobiology of the Chinese Academy of Sciences. However, Wang Ding, also from the Institute of Hydrobiology and a leading authority on the species, said that the sighting could not be confirmed 100% because of the distance, but that it looked and acted like a baiji.

Although the sighting provides a small cause for hope that the creature could survive in the wild, the outlook is not good. In the 1950s there were thousands of Yangtze River dolphins, but numbers have declined drastically due to industrial pollution, heavy river traffic and over-fishing. The last previous sighting of a wild baiji was in 2004. There are none in captivity.

The chances are that the baiji is about to join the likes of the Caribbean Monk Seal as a former resident of this planet.

The end of the Baiji

Scientists have concluded that the Yangtze River dolphin (aka baiji) is now almost certainly extinct. No trace of the dolphin was found during a recent survey of its habitat

The scientists writing in Biology Letters journal blamed unregulated fishing as the main reason behind their demise. Sam Turvey of the Zoological Society of London, one of the paper's authors, said "The Yangtze river dolphin was a remarkable mammal that separated from all other species over 20 million years ago. This extinction represents the disappearance of a complete branch of the evolutionary tree of life and emphasises that we have yet to take full responsibility in our role as guardians of the planet. While it is conceivable that a couple of surviving individuals were missed by the survey teams, our inability to detect any baiji... indicates that the prospect of finding and translocating them to a reserve has all but vanished."

The scientists added that there were a number of human activities that caused baiji numbers to decline, including construction of dams and boat collisions. However, they concluded that the primary factor was probably unsustainable by-catch in local fisheries. “Unlike most historical-era extinctions of large bodied animals, the baiji was the victim not of active persecution but incidental mortality resulting from massive-scale human environmental impacts - primarily uncontrolled and unselective fishing," the researchers concluded.

The dolphin was the only remaining member of the Lipotidae, an ancient mammal family that from other marine mammals, including over 20 million years ago. The dolphin had a long, narrow beak and low dorsal fin; lived in groups of three or four and fed on fish.

This is not the first man made extinction – other animals have been hunted to extinction (Thylacine, Great Auk, Passenger Pigeon) and it is not going to be the last (Even in Europe one in six species of mammal, including the Iberian lynx and the monk seal, is endangered). I fear we will see many more such extinctions in our lifetimes