( CNN ) -- There is something magical about animal migrations . Perhaps it 's the fact that as more of us move to cities ( The U.N. predicts that nearly 70 % of the global population will be urban dwellers by 2050 ) , the sight of congregating herds , schools of fish , or flocks of birds is increasingly rare . Or maybe witnessing animals cross great distances to eat , mate , breed and , in essence , survive helps us to take stock of our own lives . Whatever the reason , when animals come together , very often so do humans . Here 's our guide to the animal migrations that bring people out in flocks . Butterfly kingdom . Residents of Pacific Grove , California , take their butterflies very seriously . The area offers a warm micro-climate that attracts 20,000 monarch butterflies who travel up to 2,000 miles to winter in the region . In fact , the annual phenomenon has earned Pacific Grove the nickname `` butterfly town '' . `` I always hear that the monarchs are coming before I ever see one . I get emails saying , ' I saw my first monarch of the season ! ' Everyone wants to be the one to herald their return , '' says Lori Mannel , executive director of the Pacific Grove Museum of Natural History . The season sees an influx of tourists as well . During the winter months , nearly 100,000 visitors come to witness the spectacle . The last few years has seen a drastic decline in their population , a fact some credit with the degradation of milk weed -- the only flora monarchs can lay their eggs on . To help restore the population , many locals have started replanting the stuff , while the local government has instilled a $ 1,000 fine for disturbing a monarch . Where : California . When : October - February . Read more : World 's weirdest food festivals . Run , sardine , run . The east coast of southern Africa bears witness to one of the greatest migrations of all time : the sardine run . From May through July , millions of sardines spawn in the Agulhad Bank and make their way north up the coast . The migration also attracts predators , both of the human and animal variety . Each year , thousands of locals and tourists perch with massive fishing nets to catch the unwitting fish . Joining their ranks are sharks , dolphins and gannets , who also hover nearby in the hopes of snagging an easy dinner . Where : South Africa . When : May - July . Sign of the wildebeest . While tourism is n't always a welcome phenomenon for environmentalists , there are some instances where conservation efforts are abetted by traveler interest . In the Serengeti , for instance , the tens of thousands of visitors that stream in July and August for the Great Migration ( so called for the millions of wildebeests that trek from Tanzania to Kenya ) actually help to ensure funding goes to conservation . `` You could argue that tourism is one of the major reasons this huge ecosystem still exists today , '' says Craig Sholley , the vice president of philanthropy and marketing at the African Wildlife Foundation . At the peak of the migration , the banks of the Grumeti River are lined with hundreds of vehicles packed with environmental voyeurs all eager to glimpse the beasts make the life-threatening swim across the currents . Where : Tanzania and Kenya . When : July - August . Read more : World 's weirdest food festivals . Crab season . Christmas Island is perhaps best known for the swarm of red crabs that pour onto the roads and beaches every winter . `` It looks like someone came along and planted all these crabs overnight , '' explains Linda Cash , the marketing manager at Christmas Island Tourism . When the crabs come out , the atmosphere becomes positively festive , notes Cash . The roads are closed to protect the journeying numbers , and the park builds special bridges to help them cross safely . `` People come down at night with their rakes , move the crabs off the road and share a beer , '' she says . Where : Christmas Island . When : October - November . A whale of a time . As it happens , humpback whales are a species constantly on the move . This is good news for tourists , who have a plethora of choice for where and when they 'd like to engage in whale watching activities . In the summer months , Colombia 's Pacific Coast becomes a hotbed for roughly 3,000 of the journeying mammals , who use the warm waters as their mating grounds . Australia makes another popular spot to glimpse the majestic creatures , who hug the coast from July onwards . The whales can travel over 5,000 miles , and often , savvy businesses set up cruises and watch towers to help visitors get a peek . Where : Colombia and Australia . When : July - October ( Colombia ) , June - November ( Australia )
Animals migrate to breed , feed , mate , and various other essentials to survival . Sometimes , migrations attract predators , as with the sardine run in South Africa . Some communities , like in Pacific Grove , California , impose fines on anyone disrupting the local fauna . Comment: