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Acoustic communication, broadly distributed along the vertebrate phylogeny, plays a fundamental role in parental care, mate attraction and various other behaviours. Despite its importance, comparatively less is known about the evolutionary roots of acoustic communication. Phylogenetic comparative analyses can provide insights into the deep time evolutionary origin of acoustic communication, but they are often plagued by missing data from key species. Here we present evidence for 53 species of four major clades (turtles, tuatara, caecilian and lungfish) in the form of vocal recordings and contextual behavioural information accompanying sound production. This and a broad literature-based dataset evidence acoustic abilities in several groups previously considered non-vocal. Critically, phylogenetic analyses encompassing 1800 species of choanate vertebrates reconstructs acoustic communication as a homologous trait, and suggests that it is at least as old as the last common ancestor of all choanate vertebrates, that lived approx. 407 million years before present. Here, the authors record acoustic communication in 53 species commonly considered non-vocal and reconstruct acoustic communication as originating 407 million years ago.

Hatching synchronisation is widespread in oviparous taxa. It has been demonstrated that many species use sounds to coordinate synchronous hatching, being widespread among archosaurs (birds and crocodilians). Recent studies have shown that some turtle species produce vocalisations from within the egg, but the role of this behaviour in synchronising hatch is untested. The small amount of information about sound production by turtle embryos, limited to a handful of closely related species, precludes any inferences based on differences in their ecology, reproductive behaviour and phylogenetic context. With the goal to investigate if coordinated synchronous behaviour is mediated by within‐egg vocalisations in turtles, we recorded clutches from six different turtle species. The selected animals present different ecological and reproductive niches and belong to distinct phylogenetic lineages at the family level. We aimed to understand: (1) what is the phylogenetic distribution of within‐egg vocal behaviour among turtles; (2) if asynchronous turtle species vocalise from within the egg; (3) if clutch size influences synchronous behaviour and (4) if within‐egg turtle calls follow any phylogenetic signal. The new evidence provides light to the current knowledge about synchronous behaviour and within‐egg calls, challenging previous hypothesis that within‐egg sounds are accidentally produced as side‐effects of other behaviours. The study investigates the phylogenetic distribution of within‐egg vocal behaviour among turtles and its role in synchronous hatching. Clutches from six turtle species with diverse ecological and reproductive niches were recorded, aiming to understand if asynchronous species vocalise from within the egg, the influence of clutch size on synchronous behaviour and the presence of any phylogenetic signal in within‐egg turtle calls. The findings challenge previous hypotheses, suggesting that within‐egg sounds are not accidental side‐effects but may indeed mediate coordinated synchronous behaviour in turtles.

The use of drones to survey and monitor wildlife populations has increased exponentially. A common protocol used for data collection is planning flights with substantial overlap between successive photographs and lateral lines and then creating orthomosaics by merging the collected images. Because available methods for orthomosaic building assume that landscapes are static, unintended errors arise when counting moving animals. Here, we describe these sources of error and discuss potential solutions and future developments needed. Individuals can appear multiple times, be omitted or appear as faint ghosts or cut in half in the final mosaic. These errors can significantly impact abundance estimates but are rarely acknowledged. Researchers should carefully consider if using orthomosaics is really needed for surveying wildlife. Currently, there is a lack of methods to prevent these errors from arising and to explicitly accommodate them in modelling approaches. Future developments should focus on (a) creating methods to build orthomosaics that minimize these errors in the context of counting moving animals; (b) developing modelling approaches to estimate abundance while accounting for these errors; and (c) exploring alternative flight settings (e.g. amount of lateral overlap, sensor type, flight height and speed). Using an example on Giant Amazon Turtles, we illustrate potential solutions with a method for orthomosaic building that prioritizes moving animals and a modelling approach to estimate the detection errors and correct abundance estimates. The developed prototype approach for creating orthomosaics revealed many more turtle individuals than the conventional approach, although it presented more double counts as well. In the modelling approach, we found that a turtle available for detection during the survey can have a probability of 31% of being omitted or ghosted during the conventional orthomosaic building process. We also found that 12% of the turtles appearing in a conventional orthomosaic correspond to double counts. Resumo O uso de drones para amostrar e monitorar animais silvestres tem crescido exponencialmente. Um protocolo comumente usado para a coleta de dados é planejar os voos com uma considerável sobreposição entre fotos sequenciais e linhas laterais e então criar um ortomosaico através da junção de todas as imagens coletadas. Como os métodos disponíveis para a construção de ortomosaicos consideram que as paisagens são estáticas, erros inesperados surgem durante a contagem de animais em movimento. Aqui, nós descrevemos essas fontes de erro e discutimos potenciais soluções e desenvolvimentos futuros que são necessários. Indivíduos podem aparecer múltiplas vezes, serem omitidos ou aparecerem transparentes ou cortados no mosaico final. Esses erros podem afetar significativamente as estimativas de abundância, mas são raramente reconhecidos na literatura. Os pesquisadores devem considerar cuidadosamente se usar ortomosaicos é realmente necessário para amostrar animais silvestres. Atualmente, há uma lacuna de métodos para prevenir que esses erros ocorram e para explicitamente acomodar eles em abordagens de modelagem. Desenvolvimentos futuros devem focar em: (1) explorar configurações alternativas de voo (e.g., grau de sobreposição lateral, tipo de sensor, altura e velocidade de voo, etc.); (2) criar métodos para construção desses mosaicos que minimizem os erros no contexto de contagem de animais em movimento; e (3) desenvolver abordagens de modelagem para estimar abundância que levem em conta esses erros. Usando um exemplo com tartarugas‐da‐amazônia, nós ilustramos as soluções potenciais com um método para construção de ortomosaicos que prioriza animais em movimento e uma abordagem de modelagem para estimar os erros de detecção e corrigir as estimativas de abundância. O protótipo da abordagem desenvolvida para criar ortomosaicos revelou muito mais tartarugas do que a abordagem convencional, embora também tenha apresentado mais contagens duplas. Na abordagem de modelagem, nós encontramos que uma tartaruga disponível para detecção durante a amostragem tem uma probabilidade de 31% de ser omitida ou aparecer transparente durante o processo convencional de montagem do mosaico. Também encontramos que 12% das tartarugas que aparecem em um ortomosaico convencional correspondem a contagens duplas.

There is a long history of exploitation of the South American river turtle Podocnemis expansa. Conservation efforts for this species started in the 1960s but best practices were not established, and population trends and the number of nesting females protected remained unknown. In 2014 we formed a working group to discuss conservation strategies and to compile population data across the species’ range. We analysed the spatial pattern of its abundance in relation to human and natural factors using multiple regression analyses. We found that > 85 conservation programmes are protecting 147,000 nesting females, primarily in Brazil. The top six sites harbour > 100,000 females and should be prioritized for conservation action. Abundance declines with latitude and we found no evidence of human pressure on current turtle abundance patterns. It is presently not possible to estimate the global population trend because the species is not monitored continuously across the Amazon basin. The number of females is increasing at some localities and decreasing at others. However, the current size of the protected population is well below the historical population size estimated from past levels of human consumption, which demonstrates the need for concerted global conservation action. The data and management recommendations compiled here provide the basis for a regional monitoring programme among South American countries.

Recent studies have shown that acoustic signals play an important role in turtle social behavior and reproduction. We recorded embryos and hatchlings of Lepidochelys kempii inside the nest and underwater in June 2016 in Playa Santander, Veracruz, Mexico, and detected 189 sounds that were classified into 6 types according to their aural and spectral characteristics. Our results show that acoustic communication appears to be widely used in all species of sea turtles in aquatic environments, probably because of the high efficiency of this signaling modality in water compared with air.

Mercury levels in the Amazon River are generally high, but there are no published studies on Hg levels in turtles from the region. In this study, levels of Hg were examined in the muscle of six species of turtles in the Rio Negro in the Amazon basin of Brazil, including Podocnemis unifilis, Podocnemis expansa, Podocnemis erythrocephala, Podocnemis sextuberculata, Peltocephalus dumerilianus, and Chelus fimbriatus. It is important to analyze Hg levels in chelonians in this region because of the potential health risk to humans and other receptors that eat them, as well as their potential use as bioindicators. The effect of sex, weight, and carapace length on Hg concentrations in turtle muscle was examined to determine if the levels represent a health risk to riverine people. There was a significant interspecific difference in Hg levels but no differences as a function of size or gender. The highest Hg level was found in Chelus fimbriatus (mean = 432 ppb, standard deviation ± 196 ppb), followed by Peltocephalus dumerilianus (106 ± 41 ppb), Podocnemis expansa (62 ± 49 ppb), P. sextuberculata (61 ± 40 ppb), P. unilifis (35 ± 17 ppb), and P. erythrocephala (33.1 ± 17 ppb). Of the species studied, the piscivorous C. fimbriatus had the highest Hg level. Hg levels in turtles were similar to the levels found in fish from the same basin. Levels of Hg in the muscle of C. fimbriatus are sufficiently high to pose a potential risk to humans who consume them. This study represents the first comparative study of Hg levels in muscle of six species of turtles.

In the Rio Negro, the third-largest tributary of the Amazon, many turtle species have been important commercial and protein resources for centuries for populations of humans living in the region. For many years, this had been a sustainable activity, but nowadays the outlook for turtle populations in the Amazon is unfavorable due to increasing hunting pressure. Based on 20 yrs of conservation work in the Amazon, we report on the pressure faced by turtle populations in the area and report a sustainable chelonian exploitation alternative developed in the Rio Negro region. We describe the materials and the hand processing artisans use to transform natural resources into artworks. Based on this community program model, we discuss the current government support to local communities of the Rio Negro and provide insights on the application of this economic alternative to substitute for turtle commercialization in the Amazon. The outcomes of this manuscript have direct applications for environmental managers, nongovernmental organizations, and policymakers in Brazil and aim to call government and environmental managers to promote turtle conservation in the Amazon, securing economic safety for local communities.

Although turtles are well protected by laws in Brazil, the laws are not enforced in some places and ignored in others. Based on 15 years of work in the Rio Negro Basin, we describe the history of turtle exploitation in this region, comment on their current conservation status, and suggest practical conservation alternatives that are necessary to preserve stable populations.

There are only a few studies documenting acoustic communication in chelonians; here we provide additional evidence that sound plays an important role in the interchange of information in this group. We recorded 12 nests of Dermochelys coriacea during March 2012 at Barra de la Cruz Beach, Oaxaca, Mexico. Four types of sounds were identified from recordings of nests after 51 d of incubation; our results reinforce the idea that sounds are important to coordinate group behavior in turtles.

We studied the population structure, sex ratio, and abundance of a locally endangered species of freshwater turtle, the red-headed river turtle (Podocnemis erythrocephala), in the Unini River in Negro River Basin in Brazil with capture–recapture of marked individuals in 1 yr, including both dry and rainy seasons. We used trammel nets of 3 different inner mesh sizes in the lakes. The nets were revisited at 3-hr intervals from 0600 to 1800 hrs each day. All turtles were released after being marked, measured, and sexed. During the study, 352 individuals were marked including 162 males, 150 females, and 40 immatures. The majority of the turtles (79%) were captured in the dry season when the water level of the river was declining. Mean ± standard deviation straight-line carapace length was 210 ± 14 mm (range 163–262 mm) for males and 251 ± 18 mm (221–303) for females. Most turtles captured were in the intermediate size classes: 200–210 mm for males and 230–270 mm for females. The sex ratio of adults in this population was 1.05 males per female, not significantly different from 1∶1. Only 12 turtles were recaptured, each once: 5 males, 5 females, and 2 immatures. The population showed recruitment and the adults are in equilibrium; however, few turtles were captured in the smallest or largest size classes.