Turtle Assemblages Research Articles

Freshwater turtle (Reptilia: Testudines) assemblage from an urban protected Atlantic Forest remnant: population density, movement and habitat preference

ABSTRACT Urbanization may significantly impact wild population dynamics, even in protected green spaces. From 2016 to 2018, we accessed an assemblage of freshwater turtles isolated in an urban remnant of the Atlantic Forest, southern Brazil. We captured turtles by active search, hookless fishing, and funnel trap, and we marked them individually. Using a capture-mark-recapture method, we estimated population density, and movement, including home range size and habitat selection. Home ranges were estimated using the 100% minimum convex polygon method and habitat selections through eigenanalysis. We captured 41 specimens of Phrynops geoffroanus (Schweigger, 1812), 35 Trachemys dorbigni (Duméril & Bibron, 1835), and 20 Trachemys scripta elegans (Wied-Neuwied, 1839). The invasive T. dorbigni showed the highest density (1.72 individual/ha), followed by the native P. geoffroanus (1.36 individual/ha) and the invasive T. scripta elegans (0.87 individual/ha). Home range sizes for P. geoffroanus and T. dorbigni ranged between 0.04-0.48 ha, with the latter species covering the longest distance (525.8 m). All three species showed a preference for habitats influenced by human presence (walkways). Our findings highlight the anthropic influence on the movement of the freshwater turtle assemblage and underscore the need for enhanced protection of native species and control of invasive turtles. This study provides essential baseline data for future researches and management of urban areas.

Temporal changes in freshwater turtle assemblage in Gomti River, North India

Temporal changes in freshwater turtle assemblage in Gomti River, North India

Potential drivers and implications of a balanced breeding sex ratio in a small population of an imperiled species with environmental sex determination.

Small populations of imperiled species are susceptible to the negative consequences of skewed sex-ratios. In imperiled species with environmental sex determination such as sea turtles, examining sex ratios across a range of environments and population abundance levels can provide insight into factors that influence population resilience, which can then be the foci of management plans for these species. Breeding sex ratios (the ratio of actively breeding males to females during a reproductive season; BSRs) extrapolated from genetic parentage analyses are a common approach for enumerating sex ratios in sea turtles. Such analyses also allow for the characterization of multiple paternity within sea turtle clutches, which should reflect BSRs and breeding behaviors. We characterized the first BSR for a breeding assemblage of loggerhead sea turtles (Caretta caretta) belonging to the temperate, low-abundance Northern Gulf of Mexico Recovery Unit using genotypes of 16 microsatellite loci from nesting females and hatchlings. Unlike prior studies at both more-tropical and more-temperate, and higher-abundance, Recovery Units in this region, we found a balanced BSR of 1.3:1 males:female and a low incidence (~17%) of multiple paternity. This suggests that there are relatively few males breeding at this assemblage and within this Recovery Unit. Beaches in this region are expected to produce substantial numbers of male hatchlings based on sand temperature data. The relative dearth of mature males may then be due to hydrologic disturbances that disproportionately affect the fitness and survival of male hatchlings, or due to demographic stochasticity. More work is needed to study the factors that might influence male hatchling production and fitness in this region, particularly as climate change is predicted to lead to feminization in global sea turtle populations. Our work demonstrates the broad utility of characterizing BSRs and other sex ratios across a range of populations in imperiled, environmentally sensitive species.

Anthropic influence on chelonian composition in a metropolitan region of Southern Brazil

Knowledge about chelonians in Brazil remains limited, especially concerning basic research on these organisms. Considered one of the most threatened vertebrate group, chelonians are negatively affected by different factors such as anthropic pressure. Therefore, this study had two main goals: to describe the freshwater turtle assemblage within the urban and periurban area of Maringá and Sarandi, Southern Brazil, as well as to compare turtle composition between areas accessed by people and inaccessible areas. Fieldwork was conducted in six sites in 2013, 2014, 2016, 2017 and 2021, employing four different methods to record turtles. A total of five species were registered, whith two native to the region (Hydromedusa tectifera, Phrynops geoffroanus) and three exotic taxa (Trachemys dorbigni, Trachemys scripta elegans, Platemys platycephala platycephala). The most abundant species was T. dorbigni (n=162), followed by P. geoffroanus (n=140) and T. scripta elegans (n=95). To analyze the anthropic influence on the turtle composition, standardized samplings were conducted in two accessed and two inaccessible areas and Principal Coordinate Analysis (PCoA) was performed. The results revealed a strong relationship between the human presence in the areas and the occurrence of exotic turtles. The two alien taxa (T. dorbigni and T. scripta elegans) represented 74.5% of all chelonians analyzed, indicating a worrying scenario for the urban ecosystem.

Turtles for the ancestors: A zooarchaeological study of ritual deposits on Fakahina, Tuamotu archipelago (French Polynesia)

AbstractRituals and feasting ceremonies at Polynesianmaraedepict culturally complex relationships between humans and animals that cannot be explained by subsistence alone. In Central‐East Polynesia, this topic still requires the elaboration of a “ritual zooarchaeology” framework. Using sea turtle assemblages from three sacred sites on Fakahina atoll (Tuamotu), this study offers a preliminary approach to faunal deposits from ritual contexts. Following systematic excavations ofmaraeon Fakahina, analysis aimed to determine whether faunal deposits could be linked with intentional feasting and offering behaviours. To detect how ritual actions were organised through space, skeletal and taphonomic variables were examined for both overall sites and “sub‐assemblages” within sites based on the spatial associations of fauna with site features.At certain site features, derived quantitative units such as %MAU and recovery rate could identify potential offering behaviours through the intentional sorting of culturally significant body parts. The taphonomic signatures of site features could also identify open or closed deposition environments, assisting with the identification of disturbed features as either exposed platforms or enclosed cists. In addition to highlighting previously undocumented complexity in the use of site features, an overall comparison of turtle remains from the three sites shows the potential of these methods to explore variation in ritual practices.

An Evaluation of Western Chicken Turtle (Deirochelys reticularia miaria) Survey and Capture Protocols

The behaviors and activity season of Deirochelys reticularia miaria (Western Chicken Turtle) are poorly understood in Texas. Though distribution of D. r. miaria in the eastern portion of the state is widespread, turtle assemblage studies conducted within the range of the species in Texas have seldom documented its presence. There is a lack of formal protection for this subspecies and their habitat, and past research suggests that remaining habitat within the state is under threat from increasing urbanization. Therefore, the US Fish and Wildlife Service issued a 90-day finding that states listing the subspecies as threatened or endangered may be warranted. To provide survey recommendations for the western subspecies, we review species-wide capture techniques from the literature, recommend a survey season for D. r. miaria in Texas, and evaluate the efficacy and potential demographic biases of capture protocols implemented during field studies in the state in 2018 and 2019. We compared road surveys, dipnet surveys, seine surveys, night wading surveys, and two types of unbaited fyke net trap. Fyke nets were effective in every study that deployed them and captured D. r. miaria in this study at a rate of 0.25 captures per trap night. Dipnet surveys had the highest capture rate among active survey methods, but body size biases between methods were apparent. In Texas, road surveys yielded significantly lower capture rates than all other survey types. The best survey method selection will vary depending on research questions, budget, and time constraints. Utilizing proper survey protocols and understanding the activity season are crucial for performing effective studies on this species.

A new baenid, Edowa zuniensis gen. et sp. nov., and other fossil turtles from the Upper Cretaceous Moreno Hill Formation (Turonian), New Mexico, USA

We describe the first Turonian baenid turtle, Edowa zuniensis gen. et sp. nov., from the Moreno Hill Formation in New Mexico, which is located within a baenid temporal hiatus of approximately 12 million years. It was retrieved in a phylogenetic analysis as sister to the well understood basal baenodd (derived baenid) Plesiobaena antiqua from the Campanian of Montana and Alberta, with which it is morphologically similar. The two are sister taxa, forming a “Plesiobaena-grade” clade that is in a basal position within the derived clade Baenodda, outside of the two main clades of derived baenids, Palatobaeninae and Eubaeninae. Its occurrence in the middle Turonian Moreno Hill Formation suggests a southern Laramidian origin for Baenodda. The new site is (along with the Menefee Formation) younger and stratigraphically continuous with the Fruitland and Kirtland Formations, which are among the most productive Upper Cretaceous fossil sites in North America. New material of the endemic helochelydrid stem turtle Naomichelys is also described, as are several ichnotaxa on the type specimen of E. zuniensis gen. et sp. nov. The Moreno Hill Formation fossil turtle assemblage contains relict, derived, and immigrant components and is transitional between typical Early and Late Cretaceous faunas. Preliminary comparisons are made between the Moreno Hill Formation turtle assemblage and those of later San Juan Basin fossil sites, showing significantly greater baenid diversity in younger strata, the presence of trionychids throughout, and Naomichelys, which is also known from the younger Menefee Formation.

Xinjiangchelyid turtles from the Middle Jurassic of the Berezovsk coal mine (Krasnoyarsk Territory, Russia): systematics, skeletal morphology, variation, relationships and palaeobiogeographic implications

This paper is devoted to the description of a new species of xinjiangchelyid turtle – Annemys variabilis sp. nov. – represented by thousands of isolated bones and several more complete specimens from the Middle Jurassic (Bathonian) Itat Formation of the Berezovsk coal mine, Krasnoyarsk Territory, western Siberia, Russia. The description is based on a sample of the best-preserved specimens. The new species differs from other Annemys spp. by a combination of cranial and shell characters. The basisphenoids (about 200 specimens) of A. variabilis demonstrate variation in 12 characters, some of which are reported in turtles for the first time. About 20 shell characters of A. variabilis are subject to ontogenetic or interindividual variation. Some of these characters are variable in other Annemys spp. and other xinjiangchelyids. The formula of the cervical vertebrae [(2(3()4()5()6()7()8) or (2(3()4()5()6()7()8(] with two opisthocoelous vertebrae (2 and 3), four or five amphicoelous vertebrae (4–7 or 4–8), and one procoelous vertebra is unique for this species among xinjiangchelyids, which were previously known to have only amphicoelous cervicals. Other characters of the non-shell postcranium correspond to those of other xinjiangchelyids. Of the three phylogenetic analyses performed in this study, Analysis 1 does not support the monophyly of either Xinjiangchelyidae or Annemys, Analysis 2 shows paraphyly of Xinjiangchelyidae and monophyly of the Annemys clade (A. latiens, A. levensis, A. variabilis and A. wusu), and Analysis 3 supports monophyly of the Annemys clade with A. latiens, A. levensis and A. variabilis, only in the majority rule consensus tree. The diversity of the turtle assemblage of the Itat Formation is re-assessed as containing 2–3 taxa (A. variabilis [=Testudines indet. 2], Testudines indet. 1 and 3), which is in agreement with similar diversities seen in some other Middle Jurassic Asian turtle assemblages. The known record of Annemys spp. is restricted to the northern part of Asia. https://zoobank.org/urn:lsid:zoobank.org:pub:E836F02F-21DD-4A36-ACBB-4170A6CD46AD

Fossil turtles from the early Miocene localities of Mokrá-Quarry (Burdigalian, MN4), South Moravian Region, Czech Republic

Fossil turtles from Mokrá-Quarry, South Moravia Region, Czech Republic, are described in this paper. Remains come from two already known karstic fissures uncovered in Mokrá-Western Quarry (1/2001 Turtle Joint and 2/2003 Reptile Joint), as well as three new karstic fissures from Mokrá-Western Quarry (TC/2001 and 4/2018) and Mokrá-Central Quarry (3/2005). All localities correspond to the early Miocene (Burdigalian: late Eggenburgian-Ottnangian MN4). The newly described material belongs to several turtle individuals, including over 100 shell elements, so the material studied here constitutes one of the largest samples in regards of the Czech Republic fossil record. Most of these remains have been identified as Ptychogaster (Ptychogaster) sp. and Testudo (Chersine) cf. kalksburgensis Toula, 1896. However, three specimens presented here (i.e., one shell fragment and two postcranial bones) have been identified as a large tortoise (Testudinidae indet.). Turtle fauna is congruent with two ecological environments, including a dry karst landscape with open to dense steppe vegetation inferred for the heliophile testudinids, as well as freshwater masses to the semi-terrestrial ptychogasterid. Finally, this paper expands our knowledge of fossil turtle assemblages in Central Europe during the early Miocene.

Long‐term trends in marine turtle size at maturity at an important Atlantic rookery

AbstractFor species reaching maturity at a range of ages or sizes, factors that influence juvenile growth and size at maturity may have lasting impacts on overall fitness. Assessing when animals reach maturity is especially challenging for species which are difficult to follow through time as a result of highly migratory behavior, long life spans, or both. We examined nesting female size in a reproductive assemblage of green turtles (Chelonia mydas) and loggerheads (Caretta caretta) on the east coast of Florida, USA. We used a long‐term dataset from 1982 to 2019 to estimate a minimum size at maturity interval on the basis of two standard deviations below mean female size for each species. The minimum size intervals for green turtles (81.4–89.3 cm) and loggerheads (68.1–79.1 cm) were lower than most previous estimates in the literature, many of which were simply the smallest individual ever observed. There was a significant decrease in the upper bound of the minimum size interval over the study period for both green turtles (1.6 cm) and loggerheads (4.1 cm). These shifts in size at maturity may be the result of changes in population demographics, habitat quality, and behavioral reactions to these changes. The development and periodic reassessment of robust estimators of maturity are an important part of programs centered around the monitoring and conservation of vulnerable wildlife populations.

The Scontrone turtles – A new insular testudinoid fauna from the late Miocene of the Central Mediterranean

We here describe a small turtle assemblage originating from the early Tortonian (late Miocene) palaeoisland of Scontrone, central Italy, a locality previously known mostly for its endemic mammals and giant birds, which were otherwise shared only with the Gargano localities, another fossiliferous area belonging to the same palaeobioprovince. The fossil turtle remains from Scontrone are referred to the geoemydid Mauremys sp. and a so far unidentified large-sized testudinid. The biogeographic origins of the Scontrone insular chelonians are discussed. The Scontrone geoemydid adds to the known occurrences of Mauremys in the late Miocene of the Mediterranean. The Scontrone large tortoise represents the oldest known Mediterranean insular testudinid, predating significantly the well-known Quaternary endemic island tortoises of the area.

Turtle remains from the Early Cretaceous of Kut Island, Gulf of Thailand

An isolated first costal turtle plate from the Early Cretaceous of Kut Island, Gulf of Thailand, is reported and assigned to Trionychoidae gen. et sp. indet. The morphology of the plate and comparison with turtle assemblages of the Khorat Group support the correlation of the vertebrates-bearing beds of Kut Island with the Sao Khua Formation, as already suggested by the studies on sharks and dinosaurs.

Foraging Habits of Green Sea Turtles (Chelonia mydas) in the Northwestern Gulf of Mexico

Knowledge of green turtle (Chelonia mydas) foraging ecology in the northwestern Gulf of Mexico (GOM) is critical as populations begin to recover from heavy harvesting in prior centuries. We present a comprehensive long-term assessment of green turtle diets from carcasses salvaged from 1987 to 2014 along the Texas coast. Digestive tract contents were examined from 420 green turtles, ranging in size from 7.3 to 86.0 cm in straight carapace length (SCLmax). Green turtles as small as 16.2 cm SCLmaxrecruit from the oceanic environment to nearshore foraging habitat in the northwestern GOM and consume macroalgae principally. A successive shift in diet and habitat to inshore seagrasses was evident by the seagrass-dominated diet of turtles larger than 30 cm SCLmax. Animal matter remained a frequently ingested diet item suggesting these immature green turtles are better classified as omnivores. The overall evidence indicates that Texas’ recovering green turtle assemblage is exhibiting foraging plasticity within seagrass meadows changing species composition and density.

Spatial Niche Expansion at Multiple Habitat Scales of a Tropical Freshwater Turtle in the Absence of a Potential Competitor

Resource partitioning, the division of limited resources by species to help avoid competition, has been observed in freshwater turtle assemblages in several natural systems but has rarely been studied in tropical African ecosystems. Here, we investigate habitat preferences of two congeneric species in the family Pelomedusidae, Pelusios castaneus and P. cupulatta, in riverine/wetland habitats in the southern Ivory Coast (West Africa). Pelusios castaneus is a widespread species across West-central African savannahs and open forests, whereas P. cupulatta is endemic to the Upper Guinean forest region in West Africa. The two species have a similar diet composition (mainly carnivorous) but diverge considerably in body size, P. cupulatta being much larger. We use hand-fishing-nets and fishing funnel traps to record turtles in 18 distinct sites and analyze habitat preferences by species at two spatial scales. At a macro-habitat scale, P. castaneus is captured mainly in marshlands, whereas P. cupulatta is found in both rivers and wetlands. The two species differ significantly in their use of: (i) banks (P. castaneus being found primarily in spots with grassy banks, whereas P. cupulatta is found in spots with forested banks), and (ii) aquatic vegetation (P. cupulatta prefers spots with more abundant aquatic vegetation than P. castaneus), but both species select sites with no or moderate current. Additionally, in sites where P. cupulatta is not found, P. castaneus expands its spatial niche at multiple habitat scales, notably invading waterbodies with forested banks. Our results suggest that these two Pelomedusid turtle species potentially compete in the freshwater habitats in the southern Ivory Coast.

Short-term impacts of a record-shattering flood and dam removal on a river turtle assemblage and population placed within the context of a 50 year study

Long-term studies are essential for understanding how and to what extent various stressors impact long-lived species, such as turtles. Turtle populations are declining globally. Empirical data from long-term studies of turtles are largely lacking, which hinders the development of effective conservation programs. We evaluated a river turtle assemblage over a 50 year study period (1969–2019), during which the assemblage was impacted by harvesting, habitat degradation, a record-shattering flood, and the removal of a small dam. Our objective was to determine how the turtle assemblage, Graptemys geographica population (i.e., predominant species), and habitat changed in light of a recent record-shattering flood and the removal of a small dam, and place those changes within the context of other stressors documented within the 50 year study period. The record-shattering flood changed the stream and riparian habitat and, along with the dam removal, the turtle assemblage. In the short term, G. geographica and other turtle species within the assemblage, with the exception of Sternotherus odoratus, either exhibited positive or neutral impacts from the flood. We conclude that turtle species adapted to lotic habitats can cope with extreme flooding if their populations are secure prior to flooding and if the riparian and stream habitats are intact. However, as more threats simultaneously impact turtle populations, we expect fewer populations to be able to withstand such additional stressors. Within the context provided by the fifty year study period, we found that harvesting had more immediate negative impacts on the G. geographica population than did flooding.

Variation in Species Composition, Size and Fitness of Two Multi-Species Sea Turtle Assemblages Using Different Neritic Habitats

The neritic environment is rich in resources and as such plays a crucial role as foraging habitat for multi-species marine assemblages, including sea turtles. However, this habitat also experiences a wide array of anthropogenic threats. To prioritize conservation funds, targeting areas that support multi-species assemblages is ideal. This is particularly important in the Gulf of Mexico where restoration actions are currently ongoing following the Deepwater Horizon oil spill. To better understand these areas in the Gulf of Mexico, we characterized two multi-species aggregations of sea turtles captured in different neritic habitats. We described species composition and size classes of turtles, and calculated body condition index for 642 individuals of three species captured from 2011 to 2019: 13.6% loggerheads (Caretta caretta), 44.9% Kemp’s ridleys (Lepidochelys kempii) and 41.4% green turtles (Chelonia mydas). Species composition differed between the two sites with more loggerheads captured in seagrass and a greater proportion of green turtles captured in sand bottom. Turtles in sand bottom were smaller and weighed less than those captured in seagrass. Although small and large turtles were captured at both sites, the proportions differed between sites. Body condition index of green turtles was lower in sand habitat than seagrass habitat; there was no difference for Kemp’s ridleys or loggerheads. In general, smaller green turtles had a higher body condition index than larger green turtles. We have identified another habitat type used by juvenile sea turtle species in the northern Gulf of Mexico. In addition, we highlight the importance of habitat selection by immature turtles recruiting from the oceanic to the neritic environment, particularly for green turtles.

Additional records and stratigraphic distribution of the middle Eocene carettochelyid turtle Anosteira pulchra from the Uinta Formation of Utah, North America.

BackgroundAnosteira pulchra is one of two species of the obligately-aquatic freshwater clade Carettochelyidae (pig-nosed turtles) from the Eocene of North America. Anosteira pulchra is typically rare in collections, and their distribution is poorly documented. The Uinta Formation [Fm.] contains a diverse assemblage of turtles from the Uintan North American Land Mammal Age. Whereas turtles are abundantly preserved in the Uinta Fm., A. pulchra has been reported only from a few specimens in the Uinta C Member.MethodsWe describe new records of Anosteira pulchra from the Uinta Basin and analyze the distribution of 95 specimens from multiple repositories in the previously published stratigraphic framework of the middle and upper Uinta Fm.ResultsHere we report the first records of the species from the Uinta B interval, document it from multiple levels within the stratigraphic section and examine its uncommon appearance in only approximately 5% of localities where turtles have been systematically collected. This study details and extends the range of A. pulchra in the Uinta Fm. and demonstrates the presence of the taxon in significantly lower stratigraphic layers. These newly described fossils include previously unknown elements and associated trace fossils, with new anatomical information presented. This study provides insight into the taxonomy of Anosteira spp. in the middle Eocene, and suggests the presence of a single species, though no synonymy is defined here due to limits in Bridger material.

Demographics of Sympatric Musk Turtles: The Loggerhead Musk Turtle (Sternotherus minor) and Eastern Musk Turtle (Sternotherus odoratus) in a Florida Spring Ecosystem

The loggerhead musk turtle (Sternotherus minor) and eastern musk turtle (Sternotherus odoratus) are widespread species considered common throughout much of their respective ranges. Florida populations of S. minor and S. odoratus inhabit a variety of habitats, including freshwater springs and spring runs. We sampled populations of S. minor and S. odoratus from May 2000 through July 2015 as part of a long-term freshwater turtle assemblage study in a state-protected spring-run complex in central Florida. For each species, we 1) generated population estimates, 2) quantified survivorship and recruitment, and 3) calculated sex ratios, biomass, and density. Population estimates were 3417 for S. minor and 1977 for S. odoratus. Sex ratios were approximately 1:1 for both species, and density and biomass estimates were higher than most previous studies. Annual apparent survivorship was higher in male S. minor than in females, but the opposite was true for S. odoratus. Lambda values (k) suggest stable to slowly increasing populations for both species. Population growth rates for S. odoratus were equally influenced by both adult female mortality and mortality of first-year turtles, while those for S. minor were influenced by only adult female mortality. The lower fecundity values for S. odoratus may increase the importance of younger age classes in maintaining populations. Healthy populations of common species are important in maintaining overall community functions, as they often provide the base for many ecosystems. Therefore, it is prudent to promote conservation of common species to protect ecosystem structures and services.

Postnesting migration routes and fidelity to foraging sites among loggerhead turtles in the western North Atlantic

Although the western North Atlantic hosts the largest nesting assemblage of loggerhead turtles (Caretta caretta) in the world, their fine-scale habitat use beyond the nesting beach and how it effects reproductive output is still poorly understood. To characterize internesting and postnesting habitats used by loggerheads in the region, we satellite tracked 32 individual mature female turtles from a nesting beach in the southeastern Gulf of Mexico from 2009 to 2016. Thirteen of these turtles were tagged and tracked for two or more nesting seasons to assess fidelity to internesting movements, migratory pathway, and foraging site. Internesting movements for all turtles occurred over the West Florida Shelf in relatively close proximity to the nesting beach. Migratory pathways along the continental shelf led to foraging areas in four distinct regions: the southeastern Gulf of Mexico (n = 16 turtles), northeastern Gulf of Mexico (n = 8), Bahama Banks (n = 7), and Campeche Bank (n = 1). Individual turtles exhibited high fidelity to foraging sites across seasons, and 22 of the 32 tracked turtles shared overlapping foraging area utilization with at least one other individual during the tracking period. Loggerheads foraging closest to the nesting beach in the southeastern Gulf of Mexico were generally smaller than those foraging in other regions. This work highlights the importance of the West Florida Shelf for eastern Gulf of Mexico sea turtle rookeries. Identifying and managing the multiple in-water habitats used within and between nesting seasons will help sustain loggerhead turtle population recovery and maintenance.

Temporal Variation in a Turtle Assemblage Inhabiting a Florida Spring-Fed River

We conducted a survey of freshwater turtle populations in the spring-fed Ichetucknee River in northern Florida to assess temporal variation in assemblage structure. Following the same protocols as an initial 2007 survey, we hand-captured turtles while snorkeling in 2014 and found changes in species composition, abundance of 3 species, and demographic composition of 2 species. We observed a shift in the most frequently captured species from Sternotherus minor (Loggerhead Musk Turtle) in 2007 to Pseudemys concinna (River Cooter) in 2014. We attribute this shift to an increase in the abundance of adult River Cooters. Long-term studies are needed to evaluate whether the changes we observed represent trends and which environmental factors may be driving them.