Research on the effects of wildland fire and fire management on federally listed species and their habitats on San Clemente Island, Southern California
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Geology topics
Research about San Clemente Island
Source-linked reports with geographic coverage including San Clemente Island.
Interpreting the paleozoogeography and sea level history of thermally anomalous marine terrace faunas: A case study from the the last interglacial complex of San Clemente Island, California
Marine invertebrate faunas with mixtures of extralimital southern and extralimital northern faunal elements, called thermally anomalous faunas, have been recognized for more than a century in the Quaternary marine terrace record of the Pacific Coast of North America. Although many mechanisms have been proposed to explain this phenomenon, no single explanation seems to be applicable to all localities where thermally anomalous faunas have been observed. Here, we describe one such thermally anomalous fossil fauna that was studied on the second emergent marine terrace at Eel Point on San Clemente Island. The Eel Point terrace complex is a composite feature, consisting of a narrow upper bench (terrace 2a) and a broader lower bench (terrace 2b). Terrace 2b, previously dated from ∼128 ka to ∼114 ka, was thought to date solely to marine isotope stage (MIS) 5.5, representing the peak of the last interglacial period. Nevertheless, the fauna contains an extralimital northern species and several northward-ranging species, as well as an extralimital southern species and several southward-ranging species. Similar faunas with thermally anomalous elements have also been reported from San Nicolas Island, Point Loma (San Diego County), and Cayucos (San Luis Obispo County), California. U-series dating of corals at those localities shows that the thermally anomalous faunas may be the result of mixing of fossils from both the ∼100-ka (cool-water) and the ∼120-ka (warm-water) sea level high stands. Submergence, erosion, and fossil mixing of the ∼120-ka terraces by the ∼100-ka high-sea stand may have been possible due to glacial isostatic adjustment (GIA) effects on North America, which could have resulted in a higher-than-present local sea level stand at ∼100 ka. The terrace elevation spacing on San Clemente Island is very similar to that on San Nicolas Island, and we hypothesize that a similar mixing took place on San Clemente Island. Existing fossil records from older terraces elsewhere in California also show thermally anomalous elements, indicating that the scenario presented here for the last interglacial complex may have applicability to much of the marine Quaternary record for the Pacific Coast.
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Effects of roads on survival of San Clemente Island foxes
Roads generate a variety of influences on wildlife populations; however, little is known about the effects of roads on endemic wildlife on islands. Specifically, road‐kills of island foxes ( Urocyon littoralis ) on San Clemente Island (SCI), Channel Islands, California, USA are a concern for resource managers. To determine the effects of roads on island foxes, we radiocollared foxes using a 3‐tiered sampling design to represent the entire population in the study area, a sub‐population near roads, and a sub‐population away from roads on SCI. We examined annual survival rates using nest‐survival models, causes of mortalities, and movements for each sample. We found the population had high annual survival (0.90), although survival declined with use of road habitat, particularly for intermediate‐aged foxes. Foxes living near roads suffered lower annual survival (0.76), resulting from high frequencies of road‐kills (7 of 11 mortalities). Foxes living away from roads had the highest annual survival (0.97). Road‐kill was the most prominent cause of mortality detected on SCI, which we estimated as killing 3–8% of the population in the study area annually. Based on movements, we were unable to detect any responses by foxes that minimized their risks from roads. The probabilities of road‐kills increased with use of the road habitat, volume of traffic, and decreasing road sinuosity. We recommend that managers should attempt to reduce road‐kills by deterring or excluding foxes from entering roads, and attempting to modify behaviors of motorists to be vigilant for foxes.
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Characteristics of nesting areas used by San Clemente Island Sage Sparrows
I examined the nest habitat used by Sage Sparrows ( Amphispiza belli clementeae ) on San Clemente Island, one of the California Channel Islands, during March through June 1986. All nests were found in boxthorn shrubs in coastal scrub habitat. The cover of vegetation was greater and more evenly distributed at nest sites than in surrounding habitat. Nests were placed most often on the leeward side of live boxthorn shrubs interspersed by cactus.
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