Mammals quit night life after dino doom

‘Diurnal’ lifestyle

PARIS, Nov 7, (Agencies): The earliest mammals were night creatures which only emerged from the cover of darkness after the demise of the daytime-dominating dinosaurs, researchers said Monday.

This would explain why relatively few mammals follow a daytime-active or “diurnal” lifestyle today, and why most that do still have eyes and ears more suitable for living by night.

“Most mammals today are nocturnal and possess adaptations to survive in dark environments,” study coauthor Roi Maor of the Tel Aviv University told AFP.

“Monkeys and apes (including humans) are the only diurnal mammals that have evolved eyes that are similar to the other diurnal animals like birds or reptiles. Other diurnal mammals have not developed such profound adaptations.”

Maor and a team provide evidence for a long-standing theory that tens of millions of years of evading dinosaurs caused a nocturnal “bottleneck” in the evolution of mammals — the group of warm-blooded, milk-producing creatures that includes our own species.

Because they hid out in darkness for so long, possibly to avoid competition with dinos for food or territory, or being eaten by them, mammals today are not quite on par with fish, reptiles and birds when it comes to daytime vision.

Mammals, apart from primates, lack a part of the eye known as the fovea, which many fish, reptiles and birds have and is replete with photoreceptor “cone” cells for seeing colour in high light.

Instead, they tend to have more “rod” cells, which can pick up scant light in dim conditions, but provide relatively low resolution. Modern-day mammals which are active mostly by day — including types of squirrel, tree-shrews, some antelope and many carnivores — also still tend to have a keen sense of smell and acute hearing, attributes required for living in the dark.

Maor and a team analysed the lifestyles of 2,415 living mammal species, and used computer algorithms to reconstruct the likely behaviour of their ancestors, and their ancestors before them — going back to the very beginning of mammals.

Maor

The earliest mammal ancestor emerged between 220 million and 160 million years ago, evolving from a reptilian forebear. And it was probably nocturnal, according to the study published in the journal Nature Ecology & Evolution. Dinosaurs, on the other hand, were likely day-dwellers seeking out sunlight to warm their bodies like reptiles today.

The data revealed that mammals remained nocturnal throughout the Mesozoic period, which ended about 66 million years ago when a massive calamity, possibly an asteroid strike, wiped out the dinos and about threequarters of life on Earth.

Mammals, then mainly small, scurrying animals, survived, and flourished.

Most stayed nocturnal, some embraced the daytime, and others — including cats, elephants and cows — are today a bit of both.

Primate ancestors were among the first mammals to become strictly diurnal — possibly as long as 52 million years ago — the researchers found. This explains why our primate family is better adapted to the sunlit way of life — we’ve had more time to evolve and adapt.

The reason for the shift from night to day is not clear, said Maor, but may have included a “reduced risk of predation” to early mammals. The study, while showing a strong correlation between the death of dinos and the daytime emergence of mammals, cannot conclude that one led to the other.

KLAMATH FALLS,

Evolving

Also:

Oregon: Another gray wolf has been found dead in Oregon, marking the third such unsolved death of a federally protected wolf in the past year, state and federal wildlife officials said. Another wolf was shot by a hunter who claimed self-defense.

The wolf was found dead Oct 29 in Klamath County on state forest land. The US Fish and Wildlife Service has offered a $5,000 reward for information on the killing, authorities said Monday.

The wolf was known to biologists as OR-25 and was wearing a tracking collar. It was believed to have killed a calf at a private ranch near Prospect earlier this year, according to state wildlife officials.

OR-33, another collared male, was found shot dead April 23 about 20 miles northwest of Klamath Falls in Fremont-Winema National Forest. OR-28, a collared female, was found dead Oct 6, 2016, in Fremont-Winema National Forest near Summer Lake.

All three investigations remain open, and authorities do not believe the latest wolf died of natural causes, Oregon Department of Fish and Wildlife spokesman Brent Lawrence told the Mail Tribune .

Killing gray wolves in the western two-thirds of Oregon is a violation of the federal Endangered Species Act and of Oregon state game laws. The federal offense is punishable by up to a $100,000 fine, a year in jail or both. The maximum state penalty is a fine of $6,250 and a year in jail. Wolves in Oregon hunt deer, elk, bighorn sheep and goats. But they also can target livestock and are loathed by many livestock owners.

State wildlife officials say 141 livestock or domestic animals have been killed by wolves in Oregon since they began returning to the state in the late 1990s.

In 2016, wildlife officials estimated a minimum of 112 wolves lived in Oregon in 11 packs that included eight breeding pairs.

An elk hunter recently shot and killed a gray wolf in eastern Oregon in self-defense after he said the wolf charged at him while he was hunting alone and he mistook it for a coyote. The hunter, who contacted authorities after realizing he had shot a gray wolf, will not be prosecuted because the shooting was ruled self-defense.

MEXICO CITY:

Calls are mounting for the Mexican government and international experts to stop an operation to capture and enclose the few remaining Vaquita porpoises, after one of the animals died soon after being caught over the weekend.

Experts have always acknowledged the program known as Vaquita CPR would be risky.

On Monday, the experts issued a statement saying Vaquita CPR scientists will work with an independent review panel and the Mexican government to review what happened and “determine how best to proceed.”

The Animal Welfare Institute is calling for an immediate halt to the program involving the endangered porpoise species. It says that “these tiny porpoises do not respond well to the stress of capture, and not a single additional Vaquita should be deliberately put in danger in this way.”