Spring has finally arrived! Last Saturday marked the first official day of spring. Of course, as we have learned, this doesn't necessarily mean that we are done with snowy weather yet.

Despite the unpredictability of the weather, the environment around us is beginning to show hints that warmer temperatures are on the way. The days are getting longer, the grass is starting to turn greener and birds are returning from their wintering grounds in the South. But how do the birds know it is time to make the long trip back to their northern breeding grounds? And what exactly causes the annual spring baby boom that is so obvious not only in wild animals but also with the animals here at our zoo? The answers lie in the longer days, warmer weather and increased plant growth that Mother Nature so amply supplies.

In the case of migrating birds, the primary environmental signal for them to start their long trip back north is an increase in the length of daylight. These longer days have an impact on the hormones produced by their pituitary gland and begin to prepare the birds for flight. Before they migrate, birds will often experience a change in metabolism that allows for increased fat storage so they can sustain their thousand-mile trips. Migration will not actually occur until other environmental factors, such as temperature and weather conditions, begin to change as well.

Then there are those animals that have hidden underground in a deep, sleep-like state called hibernation. True hibernators need a bit of time to wake back up, since their breathing and heart rates are substantially lower when hibernating than when active. For cold-blooded animals like lizards, snakes and frogs, the primary cue to start waking up is an increase in the outside temperature. Since cold-blooded animals hibernate because their bodies cannot tolerate the lower temperatures of winter, when the thermometer goes up, their body temperature goes up as well, and they are able to crawl out of their burrows and enjoy the bounties of spring.

Spring also brings an abundance of baby rabbits, ducklings and many other animals. The reason that many animals wait until spring to bear their young is pretty obvious. Winter in Kansas can be harsh, with freezing temperatures and mounds of snow, which means there also is very little food available for the animals to eat. When spring arrives, the plants and trees begin to grow again, so there are more resources for the animals to draw from. This allows them to have enough food not just for themselves, but for their offspring.

The same holds true for the animals at the zoo. Even though our animals receive ample food during winter and have warm barns to shelter them, their instincts naturally cause them to wait until spring to have their young. For instance, it was in March of last year that our lion cubs were born. The recent birth of our pygmy slow loris on March 14 is another great example which can be seen in its exhibit in the nocturnal building. With the pygmy slow loris, however, breeding in late summer or early fall and then birthing in March is pretty typical for this animal in the wild. Then there is the brand new Bactrian camel that was born on Tuesday and the Alpaca babies we are expecting soon as well.

However, because of our unpredictable Kansas weather, it is always possible that we can have a winter storm or icy freeze even after many of the animals have returned from migration and hibernation. These weather fluctuations can definitely have a negative impact on the animals that might have returned a bit too early, but the good news is that animals can be very resilient. By burrowing into the ground or finding a nice shelter in a hollow tree, most animals are able to wait out the storm. After a few days, the snow will usually melt, the weather will warm back up and the animals will be eating, calling and reproducing again.

This is a beautiful time of year, with flowers blooming and birds singing. After being stuck inside all winter, I suggest you grab your friends, family and a picnic lunch and come visit Lee Richardson Zoo. It's the perfect way to spend a warm, breezy afternoon.

Visit our award-winning Web site at www.garden-city.org/zoo.