Octopuses (章鱼) are sea animals famous for their rounded bodies, bulging eyes, and eight long arms. They live in all the world’s oceans but there are especially more octopuses in warm, tropical (热带的) waters. Octopuses, like their cousin, the squid (乌贼), are often considered “monsters of the deep”, though some species, or types, occupy relatively shallow waters.

Most octopuses stay along the ocean’s floor, although some species are pelagic, which means they live near the water’s surface. Other octopus species live in deep, dark waters, rising from below at dawn and dusk to search for food. Crabs and shrimps rank among their favorite foods, though some can attack larger prey (猎物), like sharks. Octopuses typically drop down on their prey from above and, using powerful suctions that line their arms, pull the animals into their mouths. The octopus performs its famous backward swim by blowing up water through a muscular tube on the body called a siphon. Octopuses also crawl (爬) along the ocean’s floor, putting their arms into small openings to search for food Seals, whales, and large fish prey on octopuses.

If threatened, octopuses shoot an inky liquid that darkens the water, confusing the other animals. The octopus can also change to gray, brown, pink, blue, or green to mix with its surroundings. Octopuses may also change color as a way to communicate with other octopuses. Octopuses are solitary creatures that live alone in dens (巢穴) built from rocks, which the octopus moves into place using its powerful arms. Octopuses sometimes even fashion a rock “door” for their dens that pull closed when the octopus is safely inside.

A study was carried out as a cooperation program among researchers at the universities of Turku (Finland), Sydney (Australia) and Cordoba (Spain). Those researchers used artificial nests (人工鸟巢) to test two methods for reducing the nest predation (捕食) of endangered ground-nesting birds.

Predator control is a common challenge in areas where many animals, such as ground-nesting birds, cannot bear the impact of the increased number of predators. For example, in areas that have fewer top predators, the red fox population can be overly large for the areas they live in. Besides, predator control by hunting can be hard and cannot be carried out everywhere or at any time, for example, during the birds’ nesting season. In such cases, the foxes can cause a decline in the populations of some birds.

In the first experimental sites, the researchers spread waterfowl’s smell in wetland areas. With the chemical camouflage (伪装), the researchers studied whether predators might fail to find the artificial bird nests. In other areas, the researchers used eggs giving off an unpleasant smell which could cause discomfort with the goal of making predators believe that the bird eggs were not eatable. The researchers also used control sites which they visited as frequently as the experimental sites to stop predators from making the right choices.

The study showed that the chemical camouflage especially decreased the predation of the artificial bird nests by red foxes. “Unlike other predators, red foxes were more easily deceived into not eating bird eggs than some other predators. We found red foxes might rely more on their sense of smell to find bird nests. The chemical smells could make most of them think the food they found could not be eaten,” explains Senior Researcher Vesa Selonen from the University of Turku.

“Our results are interesting as they show that these approaches could reduce the nest predation of endangered birds. We’re wondering whether the results we observed with the artificial nests can also lead to the protection of real bird nests and a larger number of young birds,” says Professor Toni Laaksonen from the University of Turku.

All animals play. Running and rolling are ways for them to have fun. But it also seems to be how they communicate and strengthen bonds with each other.

When a dog comes up to another dog, front legs bowed or his tail high or wagging, his friend knows he wants to play. But new research shows that this play behavior is surprisingly similar when horses and dogs play.

“Up to now, most studies have focused on dog-human play due to the important implications that such studies have in understanding the special relationship we establish with our pets,” researchers from Italy wrote in the journal Behavioural Processes. “Here, we focused on social play between dogs and horses.”

To study communication among different species, Elisabetta Palagi and her colleagues from the University of Pisa found 20 YouTube videos of dogs and horses playing where their interactions lasted at least 30 seconds. They analyzed the videos, looking for specific patterns of play.

They found that while playing, both dogs and horses often had relaxed, open mouths, which is a common playful facial expression in animals. Some also copied each others' movements, like pretending to bite, playing with an object, or rolling on their backs on the ground. The team also found that the dogs and horses copied each other's facial expressions. This behavior, called rapid facial mimicry, has been seen before in dogs and sun bears, points out National Geographic. But it has never been documented between animals of different species.

“A 2000-pound horse can play with a relatively tiny dog because the two are able to communicate their intentions. It's an important study because it shows how two animals who look and behave so differently can manage to discuss how to play in a way that's comfortable for both,” Barbara Smuts, a behavioral ecologist at the University of Michigan, told National Geographic.