Body size, sex and high philopatry influence the use of agricultural land by Galapagos giant tortoises

As agricultural areas expand, interactions between wild animals and farmland are increasing. Understanding the nature of such interactions is vital to inform the management of human–wildlife coexistence. We investigated patterns of space use of two Critically Endangered Galapagos tortoise species, Chelonoidis porteri and Chelonoidis donfaustoi, on privately owned and agricultural land (hereafter farms) on Santa Cruz Island, where a human–wildlife conflict is emerging. We used GPS data from 45 tortoises tracked for up to 9 years, and data on farm characteristics, to identify factors that influence tortoise movement and habitat use in the agricultural zone. Sixty-nine per cent of tagged tortoises used the agricultural zone, where they remained for a mean of 150 days before returning to the national park. Large male tortoises were more likely to use farms for longer periods than female and smaller individuals. Tortoises were philopatric (mean overlap of farmland visits = 88.7 ± SE 2.9%), on average visiting four farms and occupying a mean seasonal range of 2.9 ± SE 0.3 ha. We discuss the characteristics of farm use by tortoises, and its implications for tortoise conservation and coexistence with people.

Linking animal migration and ecosystem processes: data-driven simulation of propagule dispersal by migratory herbivores

Animal migration is a key process underlying active subsidies and species dispersal over long distances, which affects the connectivity and functioning of ecosystems. Despite much research describing patterns of where animals migrate, we still lack a framework for quantifying and predicting how animal migration affects ecosystem processes. In this study, we aim to integrate animal movement behavior and ecosystem functioning by developing a predictive modeling framework that can inform ecosystem management and conservation. Our framework models individual-level migration trajectories between populations' seasonal ranges as well as the resulting dispersal and fate of propagules carried by the migratory animals, and it can be calibrated using empirical data at every step of the modeling process. As a case study, we applied our framework to model the spread of guava seeds, Psidium guajava, by a population of migratory Galapagos tortoises, Chelonoidis porteri, across Santa Cruz Island. Galapagos tortoises are large herbivores that transport seeds and nutrients across the island, while Guava is one of the most problematic invasive species in the Galapagos archipelago. Our model is able to predict the pattern of spread of guava seeds alongside tortoises' downslope migration range, and it identified areas most likely to see germination success and establishment. Our results show that Galapagos tortoises' seed dispersal may particularly contribute to guava range expansion on Santa Cruz Island, due to both long gut retention time and tortoise's long-distance migration across vegetation zones. In particular, we predict that tortoises are dispersing a significant amount of guava seeds into the Galapagos National Park, which has important consequences for the native flora. The flexibility and modularity of our framework allows for the integration of multiple data sources. It also allows for a wide range of applications to investigate how migratory animals affect ecosystem processes, including propagule dispersal but also other processes such as nutrient transport across ecosystems. Our framework is also a valuable tool for predicting how animal-mediated propagule dispersal can be affected by environmental change. These different applications can have important conservation implications for the management of ecosystems that include migratory animals.

Isotopic Niche Segregation among Darwin’s Finches on Santa Cruz Island, Galápagos

Darwin’s finches are a classic example of adaptive radiation involving differential use of dietary resources among sympatric species. Here, we apply stable isotope (δ13C, δ15N, and δ2H) analyses of feathers to examine ecological segregation among eight Darwin’s finch species in Santa Cruz Island, Galápagos collected from live birds and museum specimens (1962–2019). We found that δ13C values were higher for the granivorous and herbivorous foraging guilds, and lower for the insectivorous finches. Values of δ15N were similar among foraging guilds but values of δ2H were higher for insectivores, followed by granivores, and lowest for herbivores. The herbivorous guild generally occupied the largest isotopic standard ellipse areas for all isotopic combinations and the insectivorous guild the smallest. Values of δ2H provided better trophic discrimination than those of δ15N possibly due to confounding influences of agricultural inputs of nitrogen. Segregation among guilds was enhanced by portraying guilds in three-dimensional isotope (δ13C, δ15N, and δ2H) space. Values of δ13C and δ15N were higher for feathers of museum specimens than for live birds. We provide evidence that Darwin’s finches on Santa Cruz Island tend to be generalists with overlapping isotopic niches and suggest that dietary overlap may also be more considerable than previously thought.

Colored Microbial Coatings in Show Caves from the Galapagos Islands (Ecuador): First Microbiological Approach

The Galapagos Islands (Ecuador) have a unique ecosystem on Earth due to their outstanding biodiversity and geological features. This also extends to their subterranean heritage, such as volcanic caves, with plenty of secondary mineral deposits, including coralloid-type speleothems and moonmilk deposits. In this study, the bacterial communities associated with speleothems from two lava tubes of Santa Cruz Island were investigated. Field emission scanning electron microscopy (FESEM) was carried out for the morphological characterization and detection of microbial features associated with moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves. Microbial cells, especially filamentous bacteria in close association with extracellular polymeric substances (EPS), were abundant in both types of speleothems. Furthermore, reticulated filaments and Actinobacteria-like cells were observed by FESEM. The analysis of 16S rDNA revealed the presence of different bacterial phylotypes, many of them associated with the carbon, nitrogen, iron and sulfur cycles, and some others with pollutants. This study gives insights into subsurface microbial diversity of the Galapagos Islands and further shows the interest of the conservation of these subterranean geoheritage sites used as show caves.

Channel Islands National Park: Paleontological resource inventory (public version)

Channel Island National Park (CHIS), incorporating five islands off the coast of southern California (Anacapa Island, San Miguel Island, Santa Barbara Island, Santa Cruz Island, and Santa Rosa Island), has an outstanding paleontological record. The park has significant fossils dating from the Late Cretaceous to the Holocene, representing organisms of the sea, the land, and the air. Highlights include: the famous pygmy mammoths that inhabited the conjoined northern islands during the late Pleistocene; the best fossil avifauna of any National Park Service (NPS) unit; intertwined paleontological and cultural records extending into the latest Pleistocene, including Arlington Man, the oldest well-dated human known from North America; calichified “fossil forests”; records of Miocene desmostylians and sirenians, unusual sea mammals; abundant Pleistocene mollusks illustrating changes in sea level and ocean temperature; one of the most thoroughly studied records of microfossils in the NPS; and type specimens for 23 fossil taxa. Paleontological research on the islands of CHIS began in the second half of the 19th century. The first discovery of a mammoth specimen was reported in 1873. Research can be divided into four periods: 1) the few early reports from the 19th century; 2) a sustained burst of activity in the 1920s and 1930s; 3) a second burst from the 1950s into the 1970s; and 4) the modern period of activity, symbolically opened with the 1994 discovery of a nearly complete pygmy mammoth skeleton on Santa Rosa Island. The work associated with this paleontological resource inventory may be considered the beginning of a fifth period. Fossils were specifically mentioned in the 1938 proclamation establishing what was then Channel Islands National Monument, making CHIS one of 18 NPS areas for which paleontological resources are referenced in the enabling legislation. Each of the five islands of CHIS has distinct paleontological and geological records, each has some kind of fossil resources, and almost all of the sedimentary formations on the islands are fossiliferous within CHIS. Anacapa Island and Santa Barbara Island, the two smallest islands, are primarily composed of Miocene volcanic rocks interfingered with small quantities of sedimentary rock and covered with a veneer of Quaternary sediments. Santa Barbara stands apart from Anacapa because it was never part of Santarosae, the landmass that existed at times in the Pleistocene when sea level was low enough that the four northern islands were connected. San Miguel Island, Santa Cruz Island, and Santa Rosa Island have more complex geologic histories. Of these three islands, San Miguel Island has relatively simple geologic structure and few formations. Santa Cruz Island has the most varied geology of the islands, as well as the longest rock record exposed at the surface, beginning with Jurassic metamorphic and intrusive igneous rocks. The Channel Islands have been uplifted and faulted in a complex 20-million-year-long geologic episode tied to the collision of the North American and Pacific Places, the initiation of the San Andreas fault system, and the 90° clockwise rotation of the Transverse Ranges, of which the northern Channel Islands are the westernmost part. Widespread volcanic activity from about 19 to 14 million years ago is evidenced by the igneous rocks found on each island.

Nature beyond Solitude

The field notes taken for this book are not only about nature, but from nature as well. The book lets the reader peer over the author'shoulder as he takes his notes. The reader follows him to a series of field stations where he teams up with scientists, citizen scientists, rangers, stewards, and graduate students engaged in long-term ecological study, all the while scribbling down what he sees, hears, and feels in the moment. The field stations are located at Hastings Natural History Reservation, studying acorn woodpeckers; Santa Cruz Island Reserve, studying island foxes; Golden Gate Raptor Observatory, hawkwatching; H. J. Andrews Experimental Forest, recording a forest log for two weeks through the Spring Creek Project; and North Cascades Environmental Learning Center, which was built as mitigation for the environmental harm caused by the hydroelectric dam. The book explores how communal experiences of nature might ultimately provide greater depths of appreciation for the natural world.