Even though hummingbirds are the smallest birds in the world, their migrations can span hundreds or thousands of miles. While there are more than 300 hummingbird species, only a handful of them regularly migrate. Most of the hummingbirds of North America do migrate seasonally between northern breeding grounds and southern wintering grounds. Unlike many birds, however, hummingbirds migrate individually. They migrate during the day, staying low in the air to watch closely for feeding opportunities, and rest at night.

Hummingbirds can be very predictable with their migration patterns. Individual birds often migrate at the same time each year, even arriving and leaving the same yards within just a day or two. But how do they know when it is time to migrate?

Several factors affect hummingbird migration and when exactly these small birds set forth on their long journeys. The most important factor that determines the timing of hummingbird migration is daylight: the amount of daylight and the angle (角度) of the sun relative to the bird’s location. As the light levels change seasonally, hummingbirds purposefully eat more, increasing their weight by 25 to 40 percent. That extra fat will be valuable energy for their long flight.

Other factors that influence when hummingbirds migrate include:

Natural food sources: Hummingbirds will move along their migration routes as food sources appear and disappear. The most important food source is nectar-producing flowers, but the availability of insects is also a factor that can influence when hummingbirds migrate and how fast they travel.

Weather patterns: Local storms and strong winds can delay the birds’ journeys by a day or two. During spring migration, hummingbirds may be caught in bird fallouts. During poor fall weather, migrating hummingbirds may hang out in safe locations for up to a week or two to wait for better traveling conditions.

Age: Mature birds often start their migration earlier than juvenile birds. Younger hummingbirds take longer to build up their new strength before setting forth on the long migration journey.

Ants have the ability to smell out cancer cells in humans, a new study has discovered, suggesting they could be used for cancer diagnosis in future. Researchers discovered that ant species called Formica fusca has a well-developed sense of smell. It was able to distinguish cancer cells from healthy cells in humans, thanks to their sense of smell, limited trials showed. But more clinical tests must be carried out before they could be used in clinical settings like hospitals, the team said. They suggest that in future, ants could turn out to be better at dogs when it comes to locating cancer cells in humans.

To conduct their research, the scientists performed tests with 36 ants smelling cells under a lab setting.

First, the specialists exposed the ants to the smell of a sample of human cancer cells. This smell was then associated with a reward of sugar solution. In a second step, the researchers exposed the ants to two different smells. One was a new smell and the second was the smell of the cancer cells. Once this test was successful, the scientists exposed the ants to different cancer cells. As such, the scientists found that “ants can distinguish cancer cells from healthy cells and different cancer cells.”

After training, Formica fusca ant can recognize the VOC sent out by cancer cells. This isn’t the first time that scientists have used the animal sense of smell to locate cancer cells. “Dogs noses are well suited for medical diagnosis and used for the recognition of cancer,” the researchers explained. However, training them to do so requires several months to a year. “Therefore, ants, as a tool for identifying cancer cells, are fast, efficient, cheap and have strong discrimination,” the team explained. “Our approach can also be used in a range of other complex smell identification tasks in the future, including identifying drugs, explosives, spoiled foods or diseases such as malaria.”

Bats have long been one of the most feared creatures in the animal kingdom. Many pop culture associations with them are related to vampire men (吸血鬼) attacking women in order to suck their blood or witches putting evil curses on innocent individuals.

Although these associations are complete misunderstandings, bats do have a dark side as a dangerous disease medium. These flying mammals can carry a number of fatal diseases such as rabies and more recently Ebola. This has led many to wonder why we should even care about them.

Sure, there is good reason to be extremely cautious if you come into contact with bats. However, there is no denying the fact that bats play a significant role in maintaining a balanced ecosystem.

Many organic farmers have learned about the benefits of having bats nearby to help do away with amounts of pests that show up without pesticides. One brown bat, about the size of a human thumb, can consume about 600 mosquitoes and other unwanted insects within an hour. They make for a fantastic, almost essential, addition to pest management on any farm.

Even large government organizations have realized the economic benefits of bats. The United States Geological Survey estimates that bat contributions to pest management save the country at least 3.7 billion dollars per year. Without them, we would likely experience a dramatic drop in food production, which would eventually make its way into our weekly grocery bills.

As if this were not enough of an ecosystem service we receive, bats are also of great importance to a variety of plant species that are preferential to its pollination (授粉). Otherwise, these plants would decrease their ability to reproduce by at least 50 percent. A number of plant products consumed by humans fall into this preferential pollination category. Some popular foods include mangoes, bananas, peaches and guavas. Additionally, the agave plant, which is used to make tequila, is completely dependent on bat pollinators for reproduction.

Bats are major contributors to our society. These assets are in the best interest of the international community to protect and even to promote. Among significant fears housed by the general public, the fact is that we need them more than most of us imagine. And that’s why should take some measures.