The Upper Gunnison Basin (UGB), Colorado, is a montane region characterized by unusual physiography and topographic isolation. Excavations of three caves in the UGB provide one of the most diverse records of high-elevation late Quaternary vertebrates in North America. The localities, Haystack Cave (2450 m above sea level [m asl]), Cement Creek Cave (2860 m asl), and Signature Cave (3055 m asl), together provide a near-continuous record of vertebrate communities that extends from before the last glacial maximum to the present. These communities largely represent a sagebrush (Artemisia spp.) steppe-tundra environment that prevailed throughout the UGB in the late Pleistocene. At least five taxa of extinct large mammals disappear from the UGB by the Early Holocene; one small mammal (the short-faced skunk Brachyprotoma cf. B. brevimala) also became extinct. The fossil record further indicates that only four small extant mammals (Sorex preblei, Dicrostonyx sp., Lemmiscus curtatus, and Urocitellus elegans) were extirpated from the UGB by the Early Holocene, in part because of community restructuring and loss of open habitats with expansion of forests to higher elevations. An analysis of taxonomic richness and evenness at Cement Creek Cave indicates high resilience in the small mammal community despite major climate shifts over the past 40,000+ yr.

High elevation plant and animal communities are considered extremely sensitive to environmental change. We investigated an exceptional fossil record of yellow-bellied marmot (Marmota flaviventris) specimens that was recovered from Cement Creek Cave (elev. 2860 m) and ranged in age from radiocarbon background circa 49.8 cal ka BP to ~ 1 cal ka BP. We coupled isotopic and radiocarbon measurements (δ18O, δD, δ15N, δ13C, and 14C) of bone collagen from individually-AMS dated specimens of marmots to assess ecological responses by this species to environmental change over time in a high elevation basin in the Rocky Mountains of southwestern Colorado, USA. We find little change in all four isotope ratios over time, demonstrating considerable environmental stability during periods when the marmots were present. The stable ecology and the apparent persistence of the small mammal community in the cave fauna throughout the late Quaternary are in marked contrast to the changes that occurred in the large mammal community, including local extirpation and extinction, at the end of the Pleistocene.

The vertebrate fossil record of Cement Creek Cave, Colorado, spans from ≫ 45,000 yr ago to the present and represents the richest stratified series of high-elevation (≫ 2900 m) mammal remains known from the late Quaternary of North America. Stable carbon and oxygen isotope analyses of tooth enamel were used to assess potential ecological responses of two species found commonly throughout the cave, Yellow-bellied marmots (Marmota flaviventris) and Bushy-tailed woodrats (Neotoma cinerea), to late Quaternary climate and environmental changes of the Southern Rocky Mountains. Results indicate that despite such perturbations, the dietary ecologies of both species were maintained across this period. Neither taxon shifted to consuming C4 taxa or different C3 functional groups; similarly, no significant shifts in surface water use were detected. Variations in enamel δ13C were observed, however, that represent the physiological responses of high-elevation plants to changing levels of late Quaternary atmospheric CO2. While our findings extend both the geographic and elevational record of this plant CO2 response, they simultaneously highlight the ecological stability of high-elevation M. flaviventris and N. cinerea during climate changes of late Quaternary magnitude.

Haystack Cave, Gunnison County, Colorado, has provided the first collection of vertebrate remains from the Pleistocene (Rancholabrean) of western Colorado. Two carbon 14 analyses of bone apatite have produced dates of 14,935 ± 610 and 12,154 ± 1,700 years B.P. for this assemblage. This fauna, in conjunction with pollen studies, indicates the Gunnison Basin was largely unforested grassland/sagebrush shrubland in the lower basin, with open coniferous forests extending to the edges of the basin, during the late Pleistocene. The fauna also extends the known Pleistocene range of Lagurus curtatus, Phenacomys intermedius, Spilogale putorius, and Acinonyx trumani.

The ‘krill surplus’ hypothesis in Antarctica posits that the historic depletion of krill-eating whales and seals in the 18–20th centuries provided a surplus of krill in the Southern Ocean that benefited penguins. A previous study which examined stable isotopes in ancient and modern tissues of Adélie penguin (Pygoscelis adeliae) provides support for this hypothesis. Specifically, a significant decrease in δ13C and δ15N values occurred in modern versus ancient tissues from an apparent dietary shift from fish to krill associated with the purported krill surplus. Here, we present new data on gentoo penguin (Pygoscelis papua) tissues from active and abandoned colonies at three locations in the Antarctic Peninsula. We found an overall, but weak, decrease in modern versus fossil δ15N and δ13C values of gentoo penguin egg membrane with considerable variation across three breeding sites. Dietary mixing models suggest that shifts between fish and krill in gentoo penguins were likely not as strong as those previously observed in Adélie penguins. This weaker signal probably results from the greater reliance on fish in their diets, past and present, though we cannot rule out declines in primary productivity or other ecosystem shifts which also could account for declines in δ13C and δ15N values.

Investigations on the age and taphonomy of modern and abandoned penguin rookeries were completed in the Antarctic Peninsula region, 1992–1994. Systematic collection and identification of bones from modern rookeries of Adélie (Pygoscelis adeliae), chinstrap (P. antarctica), and gentoo (P. papua) penguins indicate a bias in element preservation for humeri, furcula, femora, and tibiotarsi. More than 73% of the individuals represented by these elements are juveniles. Bones from abandoned rookeries show similar patterns that can help identify old breeding sites and the species that occupied them. Radiocarbon dates completed on 13 chinstrap and Adélie penguin bones, feathers, and eggshell fragments from five abandoned rookeries suggest that occupation of these sites occurred only during warm intervals of the Little Ice Age (AD 1500–1850). These data also provide information on the paleoecology and paleobiogeography of penguins in the Antarctic Peninsula region, which help explain modern distribution patterns and demography.

Investigations in recent years of the ecological structure and processes of the Southern Ocean have almost exclusively taken a bottom-up, forcing-by-physical-processes approach relating various species' population trends to climate change. Just 20 years ago, however, researchers focused on a broader set of hypotheses, in part formed around a paradigm positing interspecific interactions as central to structuring the ecosystem (forcing by biotic processes, top-down), and particularly on a “krill surplus” caused by the removal from the system of more than a million baleen whales. Since then, this latter idea has disappeared from favour with little debate. Moreover, it recently has been shown that concurrent with whaling there was a massive depletion of finfish in the Southern Ocean, a finding also ignored in deference to climate-related explanations of ecosystem change. We present two examples from the literature, one involving gelatinous organisms and the other involving penguins, in which climate has been used to explain species' population trends but which could better be explained by including species interactions in the modelling. We conclude by questioning the almost complete shift in paradigms that has occurred and discuss whether it is leading Southern Ocean marine ecological science in an instructive direction.

We investigated 17 abandoned Adélie penguin (Pygoscelis adeliae) colonies in the Windmill Islands, East Antarctica, in summer 2002/03. Forty radiocarbon dates on penguin bones and eggshells from 13 of these sites indicate a near continuous occupation by breeding penguins in this region for over 9000 years. These dates refine the recent geological record in this region and indicate that deglaciation of the northern islands occurred much earlier than previously suggested. Dietary remains from these sites include at least 23 taxa of cephalopods and teleost fish. Quantification of these remains indicates significant fluctuations in the relative abundance of two of the more common major prey taxa. The Antarctic silverfish (Pleuragramma antarcticum Boulenger) was the most common teleost prey during all time periods represented by the ages of the sites, but preservational factors may explain a gradual decrease in the remains of this species in increasingly older sites. The most common cephalopod in the sediments was the squid, Psychroteuthis glacialis Thiele, which occurred in low numbers in most sites except one (Site 75). An unusually high number of squid beaks preserved in Site 75, dating to approximately 5700–6100 cal. yr BP, does not correlate with a decrease in fish prey at that time. The high number of abandoned penguin colonies (> 200) in the Windmill Islands may be due to population cycles in the past in association with low nest-site fidelity and movement by breeding penguins to new sites within this region.

Six abandoned colonies of Adélie penguin (Pygoscelis adeliae) were excavated near Palmer Station, Anvers Island, Antarctic Peninsula, to investigate the occupation history of this species. Sediments from each site yielded abundant fish bones and otoliths and squid beaks that represent prey remains deposited by penguins during the nesting period. Radiocarbon analyses indicate that colony occupation began prior to the Little Ice Age (LIA; 1500–1850 AD), with the oldest site dating to 644 yrs before present (BP; average reservoir-corrected date with Is range, 603–679 yr BP). Food remains indicate that the non-euphausiid prey of penguins consisted primarily of a mesopelagic squid (Psychroteuthis glacialis) and two species of fish (Pleuragramma antarcticun and Electrona antarctica). The relative abundance of the first two prey taxa varied significantly among six sites (X2>34.6; df = 10; P <0.001) with colonies dating prior to the LIA having greater representation of squid, and less of silverfish, than those occupied during the LIA. Data from control excavations at three modern colonies indicate a diet similar to that of the pre-LIA sites. These results suggest that Adélie penguins may have changed their diet in response to warming and cooling cycles in the past. In addition, only Adélie penguins are known to have nested in the Palmer Station area prior to the l950s; gentoo (Pygoscelis papua) and chinstrap (P. antarctica) penguins now breeding in this region have expanded their ranges southward in the Peninsula within the past 50 yrs, in correlation with pronounced regional warming.

This review assesses the circumpolar occurrence of emerged marine macrofossils and sediments from Antarctic coastal areas in relation to Late Quaternary climate changes. Radiocarbon ages of the macrofossils, which are interpreted in view of the complexities of the Antarctic marine radiocarbon reservoir and resolution of this dating technique, show a bimodal distribution. The data indicate that marine species inhabited coastal environments from at least 35 000 to 20 000 yr BP, during Marine Isotope Stage 3 when extensive iceberg calving created a ‘meltwater lid’ over the Southern Ocean. The general absence of these marine species from 20 000 to 8500 yr BP coincides with the subsequent advance of the Antarctic ice sheets during the Last Glacial Maximum. Synchronous re-appearance of the Antarctic marine fossils in emerged beaches around the continent, all of which have Holocene marine-limit elevations an order of magnitude lower than those in the Arctic, reflect minimal isostatic rebound as relative sea-level rise decelerated. Antarctic coastal marine habitat changes around the continent also coincided with increasing sea-ice extent and outlet glacial advances during the mid-Holocene. In view of the diverse environmental changes that occurred around the Earth during this period, it is suggested that Antarctic coastal areas were responding to a mid-Holocene climatic shift associated with the hydrological cycle. This synthesis of Late Quaternary emerged marine deposits demonstrates the application of evaluating circum-Antarctic phenomena from the glacial-terrestrial-marine transition zone.

Sixty-three radiocarbon dates on organic remains from 21 abandoned colonies of chinstrap (Pygoscelis antarctica) and Adélie (P. adeliae) penguins on 12 islands in the Antarctic Peninsula region are evaluated for determining the occupation history of penguins in this region. This record also provides a means for assessing sea-level change, glacial advances and retreats, and population responses by penguins to these events. All conventional dates were corrected for the marine-carbon reservoir effect by applying a ΔR = 700±50 BP and marine calibration curves. The 63 calibrated dates give 2σ ranges (95% confidence intervals) from modern to 5990 yr BP. These dates indicate progressively older occupations from north to south along the Antarctic Peninsula. No sites older than approximately 540 BP occur in the northern peninsula, either because they have not yet been found or older sites have been destroyed by solifluction and glacial scouring. Three dates from one locality near Rothera Point, Adelaide Island, also were calibrated with a ΔR = 750 ± 50 and 800 ± 50 BP. No difference was found between calibrated dates using these two other ΔR values, indicating that local corrections for variation in upwelling intensity may not be necessary.

Non-krill prey remains were recovered from ornithogenic sediments at three active Adélie penguin colonies on Ross Island, to assess long-term dietary trends in this species. Radiocarbon dates place the age of these deposits from a maximum of 947 years ago to the present. We identified 12 taxa of fish and two of squid with the Antarctic silverfish (Pleuragramma antarcticum) as the most abundant prey species represented at all sites. In addition, silverfish have decreased in importance in Adélie penguin diet over the past 600 years, perhaps in response to climate change since the onset of the Little Ice Age, though it remains much more abundant in current penguin diet in the Ross Sea than in the Antarctic Peninsula. Other prey taxa reflect the diversity of prey selection by Adélie penguins in Antarctica.

The long-eared owl (Asio otus) and short-eared owl (A. flammeus) are indistinguishable by bone morphology alone. Since they inhabit contrasting ecological situations, identification of their bones from prehistoric sites is important for paleoenvironmental interpretations. Measurements on long bones of modern specimens indicate these species can be identified by bone size. Tables are presented for use by the analyst in identifying complete or fragmentary wing and leg bones.

Excavations at Pottery Mound, a large Pueblo ruin located on the banks of the Rio Puerco in New Mexico, have recovered over 4,000 bird bones representing 50 species. The habitats of these birds include grassland, marshland, canal- and riverbank, Pinyon-juniper forest, and coniferous forest. Instead of attributing this diversity to changing climate or long-distance hunting expeditions away from the pueblo, I employ the "garden hunting" model, which ascribes increased species biomass to areas of human disturbance. At Pottery Mound prehistoric agricultural fields increased insect populations and provided wild and cultivated seeds which attracted a variety of birds. Additionally, irrigation canals extended riparian growth from the river across the floodplain creating more available cover for predators. This ecotone effect allowed avian species to increase beyond their normal numbers and diversity in undisturbed areas. All 50 species at Pottery Mound could have been obtained within a small radius of the site.