Galapagos Daily: Measuring evolution

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The rocky islet of Daphne Major viewed from North Seymour Island. In 1973, Peter and Rosemary Grant of Princeton University began a decades-long study of the finches living on Daphne Major. They banded and measured every finch on this island laboratory, measuring heritable traits such as beak size, and documenting how seasonal variation rolled the dice in a game of life or death for its feathered inhabitants. Drought years caused a shift in beak sizes among finches as the larger beaks were better adapted to open the harder, armed seeds that were the only food left. Birds with larger beaks survived and reproduced, the next generation had larger average beaks. Evidence of natural selection and evolution, measured over decades one beak at a time.

The rocky islet of Daphne Major juts above the Pacific as seen from North Seymour Island. In 1973, Peter and Rosemary Grant of Princeton University began a decades-long study of the finches living on Daphne Major. They banded and measured every finch on this island laboratory every year, measuring traits that can be passed down, such as beak size. Through time and generations of finches, they documented how seasonal variation rolled the dice in a game of life or death for its feathered inhabitants. Drought years caused a shift in beak sizes among finches as the larger beaks were better adapted to open the harder, armed seeds that were the only food left on this desert island. Surviving birds had larger beaks, they reproduced, and the next generation had larger beaks. Evidence of evolution by natural selection, measured over decades one beak at a time.

 

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Galapagos Daily: Sally Lightfoot Crabs

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Galapagos Daily: Sally Lightfoot Crabs

Are the two crabs in the photo the same species? My Science Olympiad kids guessed no, but they are both Sally Lightfoot crabs (Grapsus grapsus), found everywhere along the rocky shores of the Galapagos. Young crabs are black to blend in to the lava rocks and escape predation, while the larger adult crabs can sport their bright colors without fear of being eaten. Sally Lightfoots are important scavengers of rocky shore communities, found on the Pacific coasts of the Americas from northern Peru to Mexico.
John Steinback wrote during his travels in the Sea of Cortez, “These little crabs, with brilliant cloisonné carapaces, walk on their tiptoes, They have remarkable eyes and an extremely fast reaction time…they are exceedingly hard to catch. They seem to be able to run in any of four directions; but more than this, perhaps because of their rapid reaction time, they appear to read the mind of their hunter…If you walk slowly, they move slowly ahead of you in droves. If you hurry, they hurry. When you plunge at them, they seem to disappear in a puff of blue smoke—at any rate, they disappear. It is impossible to creep up on them. They are very beautiful, with clear brilliant colors, red and blues and warm browns.”

 

 

 

Galapagos Day 7: Great frigate birds

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Frigate bird (Fregata minor) mating ritual on North Seymour Island. The male inflates a red pouch at his throat to attract a female.

Great frigate bird (Fregata minor) mating ritual on North Seymour Island. The male inflates a red pouch at his throat to attract a female. Frigate birds have the largest ratio of wing span to body mass, thought to aid them in remaining aloft for long periods above the sea as they hunt flying fish, squid, and other fish.

This downy chick is about 3 weeks old. Parents take turns hunting and caring for their single chick.

This downy chick is about 3 weeks old. Parents take turns hunting and caring for their chick for a period of 4-6 months, the longest period of parental care for any bird.

Parents feed their young by regurgitating fish. We watched for several minutes as other frigate birds swooped in, hoping to steal free food, before the mother opened her beak to feed her young.

Parents feed their young by regurgitating fish. We watched this mother and chick for several minutes as other frigate birds swooped in, hoping to steal free food, before the mother opened her beak to feed her chick.

 

 

Galapagos Daily: Holy prickly pear cactus, Batman!

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Imagine my surprise and delight to walk the pathway to Tortuga Bay on Day 2 and discover a forest of giant prickly pear cacti (Opuntia gigantea)! On islands with land iguanas, like Santa Cruz, this species of cactus (1-3 ft. tall elsewhere in the world), grows to tree-like proportions to avoid being eaten. Tree-like, because it is not a woody plant--instead, the cactus pads flatten and thicken into something resembling a trunk.

Imagine my surprise and delight to walk the pathway to Tortuga Bay on Day 2 and discover a forest of giant prickly pear cacti (Opuntia gigantea)! On islands with land iguanas, like Santa Cruz, this species of cactus (1-3 ft. tall elsewhere in the world), grows to tree-like proportions to avoid being eaten. Tree-like, because it is not a woody plant–instead, the cactus pads flatten and thicken into something resembling a trunk. Yet another Galapagoan example of a species responding to challenges in their environments.

Galapagos Day 6: Small-scale farming

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Subsistence agriculture has always been a part of life in the Galapagos, but it is rapidly being replaced by tourism. We visited a small family farm today to see how sugar cane and coffee were traditionally grown and harvested. Here we learned how a donkey or people can extract the juice from sugar cane. We then walked into a sugar cane grove to see how they planted it, and sampled brown sugar, coffee, and moonshine.

Subsistence agriculture has always been a part of life in the Galapagos. Today, we visited a small family farm to see how sugar cane and coffee were traditionally grown and harvested. Here we learned how a donkey or people can manually extract the juice from sugar cane, though the process is now mechanized. We then walked into a sugar cane grove to see how it was grown, and sampled brown sugar, coffee, and moonshine. Today, most of the products from this farm are sold on-site, as the family discovered ecotourism to be more lucrative. Despite the desire for self-sufficiency, the Galapagos are shifting to a service economy as tourism grows. In talking with our Isabela guide, we learned that there is tension between locals and tour companies, particularly cruises, that come to the Galapagos for the resources but contribute little toward the local economy. Our study abroad tour puts much-needed money into the economy as the tour leaders arrange for us to stay on-site, eat at local restaurants, and hire local guides. During our travels today, our guide stopped at a small bakery to buy cinnamon and chocolate bread and again at a small farm to buy three watermelons.

Galapagos Day 5: Galapagos penguins!

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The only penguins found in the northern hemisphere are endemic Galapagos penguins (Spheniscus mendiculus). Unlike their arctic brethren, Galapagos penguins must adapt to heat since their population straddles the equator. Besides cooling themselves in the water, they hunch over to shade their feet and pant like dogs to cool their throats and nasal passages.
Galapagos penguin populations decline in El Nino years, when sea temperatures remain warm and food (small fish like sardines) becomes scarce. The penguins’ breeding cycle is driven by sea surface temperatures, and they often do not breed at all in El Nino years. In addition, invasive dogs, rats and cats eat the eggs and destroy their nests. Our guide told us that scientists worry that the current population could not survive another El Nino. With fewer than 1000 breeding pairs, the Galapagos penguin is the rarest penguin in the world.