PG3C. Stay Current—Population Reproduction, Growth, and Change Over Time

cover for GSS book Population Growth

Staying current for Chapter 3

{ Population Growth Contents }

2024-01-05. Protecting and connecting landscapes stabilizes populations of the Endangered savannah elephant. [] By RYAN M. HUANG , CELESTÉ MARÉROBERT A. R. GULDEMOND , STUART L. PIMM, AND RUDI J. VAN AARDEA, Science. Excerpt: African savannahs cover …almost half of the continent, of which 10% is protected (1) and …16% sustain globally Endangered savannah elephants (Loxodonta africana) (2). These savannahs are also home to half a billion people, leading to high levels of human-wildlife conflict. …conservation “fortresses,” creates relatively small, isolated habitat islands that keep elephants in and humans out. This separation reduces human-wildlife conflict (3) but limits dispersal since fences or adjacent human-dominated landscapes prevent movement. An alternative solution found throughout southern Africa is clusters of well-protected areas …that form a core area connected to less-protected buffer areas …that allow for human activities (4). …Elephant population growth rates across southern African protected areas follow several patterns: …Across sites, more strictly protected areas…hold populations that typically grow and are much less likely to show sharp declines than populations in buffer areas…. In regions with historically high incidences of poaching, protection appears to prevent population declines. Protected sites also show more consistent changes in numbers from year to year than buffer areas….

2022-06-09. ‘Fantastic giant tortoise’ species thought extinct for 100 years found alive. [] By Sofia Quaglia, The Guardian. Excerpt: A rare Galápagos species, the “fantastic giant tortoise”, long thought extinct, has been officially identified for the first time in more than a century in what scientists called a “big deal” for the famed islands’ embattled biodiversity. The animal is the first Chelonoidis phantasticus to be seen since a male specimen was discovered by the explorer Rollo Beck during an expedition in 1906. The newcomer has been named Fernanda, after the Fernandina Island, a largely unexplored active volcano in the western Galápagos Archipelago that she calls home.…

2020-03-08. Exponential growth and epidemics. Source: https://www.3blue1brown.com Excerpt: A good primer on exponential and logistic growth. []  

2019-04-30. Imported wolves settle in as Lake Superior island teems with moose. By Christine Mlot, Science Magazine. [] Excerpt: Thirteen new radio-collared wolves are now scouting Isle Royale in Michigan and feasting on moose, whose numbers this winter reached 2060—the second highest estimate since ecologists began to study predators and prey on the island in 1958. The new wolves, imported to help restore the U.S. national park from overbrowsing by moose, are largely avoiding the territory of the remaining two wolves of the original population. Twenty female moose are also sporting radio collars, allowing biologists to watch both wolf and moose movements online. After 8 years essentially unfettered by predation because wolf numbers were so low, the moose population has been booming at 19% a year, according to data released today by Michigan Technological University (MTU) in Houghton. The new wolves are expected to check moose numbers and help restore balsam fir and other plants, according to National Park Service (NPS) planners. And the flood of GPS data is revealing “stuff we’ve never seen before,” says MTU wildlife ecologist Rolf Peterson, such as where moose congregate to feed on new spring growth. Peterson and his colleagues plan to chemically analyze the specific balsam fir trees moose eat to determine whether they choose twigs with compounds that may have anti-inflammatory properties….

2018-12-08. Seeking Clues to Longevity in Lonesome George’s Genes. By Steph Yin, The New York Times. [] Excerpt: The giant tortoise lived for more than a century, carrying genes linked to a robust immune system, efficient DNA repair and resistance to cancer. When Lonesome George, the only survivor of the Pinta Island tortoises of the Galápagos, died in 2012, the news landed with a blow. Rationally, people had time to prepare for the reality that George would one day fade away, and with him, an entire lineage. He had lived for a century or more, a common life expectancy for giant tortoises, and all attempts to mate him during his last few decades were unsuccessful. But emotionally, it’s hard to brace oneself for the realization that something that was once there is finally, completely gone. It’s the kind of stuff that makes you ponder life, our fleeting stint in the universe and the unrelenting, forward march of time.m Similar feelings drive longevity research. Recently, a team of scientists turned to George for help in this search, mining his genetic code for clues to his long life span. In a paper published Monday in Nature Ecology & Evolution, the researchers reported preliminary findings of gene variants in George linked with a robust immune system, efficient DNA repair and resistance to cancer. The study also sets the stage for understanding giant tortoises’ evolutionary past, which might help to conserve them in the future….

2017-03-11. Meet Diego, the Centenarian Whose Sex Drive Saved His Species.By Nicholas Casey, The New York Times. Excerpt: By fathering hundreds, a giant tortoise in the Galápagos Islands reversed the threat of extinction. Another, earning the name Lonesome George, was unable to do the same. …Then came Diego, returned to the Galápagos in 1977 from the San Diego Zoo. …The tales of Diego and George demonstrate just how much the Galápagos — a province of Ecuador — have served as the world’s laboratory of evolution. So often here, the fate of an entire species, evolved over millions of years, can hinge on whether just one or two individual animals survive from one day to the next. …Abingdonii and hoodensis were easy prey for the buccaneers and whalers who poured onto their islands in previous centuries and saw only defenseless, slow-moving meals that could easily be carted away. Nor did it help that the giant tortoises of the Galápagos can survive for up to a year in the hull of a ship, meaning they provided a near-endless supply of fresh meat as they were stacked below decks by the hundreds. They were even tossed overboard when a ship needed to lose ballast for a quick getaway. …Among those who dined on giant tortoise flesh: Charles Darwin. “We lived entirely on tortoise meat, the breastplate roasted … with flesh on it, is very good; and the young tortoises make excellent soup,” Darwin wrote in 1839, near the peak of the tortoise plunder in which some 200,000 were killed or carried away from the islands….

2015-10-21. New Species of Galápagos Tortoise Is Identified. By Pam Belluck, The New York Times. Excerpt: For the first time in more than a century, scientists have identified a new species of Galápagos tortoise, the grand giants of the Pacific archipelago that helped inspire Darwin’s theory of evolution. …“Now the genetics has put some real evidence that says the simple explanations don’t hold, that some of the islands have tortoises that arrived at different times from different islands,” said Oliver Ryder, director of genetics at the San Diego Zoo’s Institute for Conservation Research, who was not involved in the new discovery. “The recognition of this separate evolutionary history I think will be very important.”… 0

2013-07-18.  Last-of-Its-Kind Tortoise Gets Royal Treatment from Taxidermists [Slide Show].   Excerpt: Preserving an iconic animal like Lonesome George is all about the details. Eleanor Sterling happened to be visiting the Galápagos Islands on June 24, 2012, the day Lonesome George died. George, the last of a species of giant tortoise unique to Pinta Island, had become an iconic symbol of the struggle to conserve disappearing species. Sterling had come to the islands on conservation business, but she dropped everything when she heard that George had expired. The first thing Sterling did was put in a call to George Dante, a New Jersey taxidermist. Sterling, who directs the American Museum of Natural History (AMNH) Center for Biodiversity and Conservation in New York City, knew Dante from his previous work for the museum. He impressed on her the need to act quickly to protect the iconic tortoise’s body from the ravages of decay. George’s eyes and the skin, being most prominent, were particularly vulnerable. That turned out to be no easy matter on Pinta, one of the smaller and more remote islands in the archipelago. Sterling and members of Galapágos National Park Service began to search local stores for freezer plastic or some other material to wrap George in. …Dante unwrapped George and waited for him to defrost. He and his team of four taxidermists then began to take dental alginate and silicone molds of George’s feet and head. The taxidermists then poured polyester resin into the negative molds to create three-dimensional models. The models will be used for reference throughout the six-month or so process of being stuffed and mounted…. Sophie Guterl, Scientific American.

2012 July 02. A Giant Tortoise’s Death Gives Extinction a Face. By Carl Hulse, The NY Times. Excerpt: George, the last giant tortoise of his subspecies in this archipelago, was found dead in his corral at the Charles Darwin Research Station here the morning of June 24 — to the shock of his devoted caretakers, who had hoped he would survive for decades to continue his line…The Galápagos is home to other types of giant tortoises, though their numbers remain low and their populations vulnerable…“We were expecting to have George another 50 years,” he said as he stood before the pen, which houses a heart-shaped pool in which the tortoise’s caretakers had hoped to entice him to produce an heir with two biologically close female tortoises who remain. “It feels kind of empty.” George’s death was a singular moment, representing the extinction of a creature right before human eyes — not dinosaurs wiped out eons ago or animals consigned to oblivion by hunters who assumed there would always be more….

2012 Jan 9.  ‘Extinct’ tortoise likely still exists, scientists say. CBC News. Excerpt: Dozens of giant tortoises belonging to a species believed extinct for 150 years may be living in a remote part of the Galapagos Islands, scientists believe…In 2008, a team of Yale researchers took blood samples from more than 1,600 tortoises living on Volcano Wolf on the northern tip of Isabela Island — more than 300 kilometres from Floreana. After comparing the samples to a genetic database of living and extinct tortoise species, they detected the genetic signatures of C. elephantopus in 84 Volcano Wolf tortoises, meaning one of their parents was a purebred member of the missing species. In 30 cases, breeding had taken place in the last 15 years, and since the lifespan of tortoises can exceed 100 years, there is a high probability that many of the purebreds are still alive, researchers said….

2010 March 18. As Southwest Wolf Recovery Effort Struggles, Northern Rockies Packs Multiply — a Tale of 2 Populations. By April Reese, NY Times. Excerpt: GILA NATIONAL FOREST, N.M. — On a rise above Copperas Creek, a flash of white captures Michael Robinson’s eye. In the shadow of a ponderosa pine, a single deer antler lies atop the turmeric-hued soil. “Wolf food,” he says, bending down to take a closer look.
All that’s missing, says Robinson, a conservationist with the Center for Biological Diversity, are the wolves. This rocky, pine-scattered ridge lies in the heart of the Blue Range Wolf Reintroduction Area, a 7,000-square-mile wild haven for Mexican gray wolves, which were reintroduced here 12 years ago after gaining federal protection under the Endangered Species Act in 1976.
Yet despite evidence of ample prey here, and an open invitation from the Fish and Wildlife Service to inhabit the Gila, no wolves occupy this part of the forest. In fact, only 15 wolves are found in the New Mexico portion of the reintroduction area, which extends several hundred miles west into southeastern Arizona. About 1,000 miles north, in the northern Rockies, the story of the Mexican wolf’s larger cousins is a far different one.
In the Greater Yellowstone Ecosystem…gray wolves are flourishing after FWS reintroduced them in 1995. Today, about 1,700 gray wolves roam the northern Rockies region compared to a handful in 1994….
…Why are Mexican wolves still struggling in the Southwest 12 years after the first animals were released into the wild, while wolves reintroduced to the northern Rockies ecosystem three years earlier have made a successful comeback?
The reasons are many, experts say, ranging from diverging policy decisions to geography and economics…. 

2008 October 7. Future of Giant Turtle Still Uncertain. By Jim Yardly, The New York Times. Excerpt: …Scientists trying to save one of the world’s most endangered species of freshwater turtles say waiting is their only recourse after a complicated attempt to mate two elderly turtles during this year’s breeding season ended without producing any offspring.
The fate of the Yangtze giant soft-shell turtle seems especially uncertain because only one female is known to exist — an 80-year-old turtle with a leathery shell that lived without notice for a half century inside a zoo in Changsha, the capital of Hunan Province, in southern China. Only when scientists discovered her existence last year did it become clear that a chance remained to save her species.
In May, scientists drove her more than 600 miles to a zoo in the city of Suzhou. There, a male turtle estimated to be 100 years old awaited her. He had been the last known male of the species, though in recent months scientists discovered two more males in Vietnam.
…The female produced roughly 100 eggs and about half appeared to be fertilized. But scientists now say the embryos apparently died in early development….
…Xie Yan, the China program director for the Wildlife Conservation Society, said she remained hopeful.
…“The male and the female didn’t spend enough time together this year,” she said. “This was the first time they mated. Next time will be better.”… 

2008 August 7. VIDEO: Lonesome George a Father? National Geographic. The last of his species, the giant tortoise Lonesome George has fertilized 11 eggs with 2 females at his home on one of the Galápagos Islands, scientists say. 

2007 November 10. Giant Galapagos Reptiles on Slow Road to Recovery. Bryn Nelson, Science News. Not far from where the Galapagos Islands’ most famous loner spends his days, tourists disembark by the inflatable boatload at a modern dock. A … walkway leads to a natural enclosure sheltering a misanthropic Galapagos tortoise named Lonesome George.
The confirmed bachelor has been a potent icon of conservation ever since he was spotted on remote Pinta Island in 1971 … Now in his 60s, 70s, or beyond – no one really knows – George may have lived more than half his life in exile. He is quite likely the world’s last pure-bred Pinta tortoise …
Last April, however, the surprise discovery that Lonesome George has a genetic cousin on another island cast doubt, in a hopeful way, on George’s one-of-a-kind status. The revelation is just one illustration of how genetics and conservation biology are intermingling to rewrite an oversize reptile’s evolutionary past and to reshape plans to safeguard the remaining tortoise species well into the future. 

2007 May 8. A Lonesome Tortoise, and a Search for a Mate. By JOHN TIERNEY, NY Times. Excerpt: When I met Lonesome George two decades ago, in his pen on the main island of the Gal‡pagos, I had the usual impulse to fix up the world’s most famous bachelor…. I didn’t find her, of course, so I went back to George’s pen to bid a sad farewell to him and his species. Then I penned a long – and quite moving, I thought – contemplation of the ethics of conservation, the destructiveness of man and the meaning of life. Now it seems the obituary was premature. … Last week, after sampling the genes of a few tortoises on Isabela Island, biologists announced that there is probably at least one Pinta tortoise somewhere among the thousands of tortoises there. Next year the researchers hope to find a female to take back to George’s pen.
…George is not what you would call a stud. When I visited him in 1985, he was thought to be a relatively young adult, maybe 50 years old, but he was already a confirmed bachelor. He hadn’t shown any interest in two females of a similar species placed in his pen. One had flipped over and drowned in the wading pool. The keepers weren’t positive that George had driven this tortoise to her death, but he definitely hadn’t been doing any Barry White serenades.
A few years later, in 1993, there was briefly a companion known as “Lonesome George’s girlfriend,” but she was not a tortoise. She was a 26-year-old graduate student in zoology from Switzerland named Sveva Grigioni. By coating her hands in the genital secretions of female tortoises and gently stroking him, she managed to demonstrate a couple of times (in the course of several months’ work) that George was capable of an erection. But whereas her touch could induce other male tortoises to reach orgasm within a few minutes, with George she never managed to collect any sperm. …”He started to try copulation,” Ms. Grigioni said, “but it was like he didn’t really know how to.” To be fair to George, he’s never been observed with a female of his race, Geochelone nigra abingdoni….The tortoise populations in the Gal‡pagos were devastated first by hungry whalers and pirates, and then by museum collectors who were far more energetic than the sailors in scouring the islands for the few remaining animals. Until George was discovered, the last tortoises seen alive on Pinta were the ones captured and killed a century ago by an expedition from the California Academy of Science….

3 June 2005. For Fruit Flies, Gene Shift Tilts Sex Orientation. By ELISABETH ROSENTHAL, International Herald Tribune. When the genetically altered fruit fly was released into the observation chamber, it did what these breeders par excellence tend to do. It pursued a waiting virgin female. It gently tapped the girl with its leg, played her a song (using wings as instruments) and, only then, dared to lick her – all part of standard fruit fly seduction. The observing scientist looked with disbelief at the show, for the suitor in this case was not a male, but a female that researchers had artificially endowed with a single male-type gene. That one gene, the researchers are announcing today in the journal Cell, is apparently by itself enough to create patterns of sexual behavior – a kind of master sexual gene that normally exists in two distinct male and female variants. In a series of experiments, the researchers found that females given the male variant of the gene acted exactly like males in courtship, madly pursuing other females. Males that were artificially given the female version of the gene became more passive and turned their sexual attention to other males. …The finding supports scientific evidence accumulating over the past decade that sexual orientation may be innately programmed into the brains of men and women. Equally intriguing, the researchers say, is the possibility that a number of behaviors – hitting back when feeling threatened, fleeing when scared or laughing when amused – may also be programmed into human brains, a product of genetic heritage. “This is a first – a superb demonstration that a single gene can serve as a switch for complex behaviors,” said Dr. Gero Miesenboeck, a professor of cell biology at Yale.