Jeffrey William Lang

• PhD Ecology U. Minnesota
• Professor Emeritus at University of North Dakota

Incubation temperature determines sex in the mugger crocodile, Crocodylus palustris. Exclusively females are produced at constant temperatures of 28.0°C through 31°C. At 32.5°C, only males are produced. Both sexes are produced in varying proportions at 31.5, 32.0, and 33.0°C. Embryo survival is not affected within this range, but developmental rate...

The gharial Gavialis gangeticus is a Critically Endangered crocodylian endemic to the Indian subcontinent. The species has experienced a 95% population decline over the past 2 centuries. The largest self-sustaining population inhabits the protected National Chambal Sanctuary (NCS) in north India and represents >80% of extant gharials globally. We d...

Details of varied activities Gharial Ecology Project during 2021-2022 summary May 2023

Over half of all crocodylians are threatened with extinction, with many species considered to be functionally extinct throughout their historical ranges. How such losses impact crocodylian functional diversity (FD) and its conservation is poorly understood, but can be investigated using measurable traits. Where such information is unavailable, phyl...

Wild animals are captured or taken opportunistically, and the meat, body parts, and/or eggs are consumed for local subsistence or used for traditional purposes to some extent across most of the world, particularly in the tropics and subtropics. The consumption of aquatic animals is widespread, in some places has been sustained for millennia, and ca...

The Critically Endangered gharial ( Gavialis gangeticus ) residing within Bardiya National Park (BNP) in Nepal constitutes the sixth major sub‐population of this unique lineage; however, this population is not well studied. A 46 km protected stretch of the Babai River and a 60 km stretch of the Karnali River in and around BNP were surveyed for ghar...

The gharial (Gavialis gangeticus) is a critically endangered, long‐snouted crocodilian, endemic to the Indian sub‐continent. Today, the species' distribution and numbers have reduced by more than 95% in all the large rivers where it was formerly abundant. Living upstream in a reservoir dammed in 1976, the Katerniaghat gharial population has continu...

The gharial ( Gavialis gangeticus Gmelin) is a fish-eating specialist crocodylian, endemic to south Asia, and critically endangered in its few remaining wild localities. A secondary gharial population resides in riverine-reservoir habitat adjacent to the Nepal border, within the Katerniaghat Wildlife Sanctuary (KWS), and nests along a 10 km riverba...

Gharial (Gavialis gangeticus) is listed as critically endangered, and the historical range loss suggests severe genetic bottleneck events that might have occurred in the remnant populations. We used 14 species-specific microsatellite markers to investigate the genetic diversity of the largest breeding population of gharials in Chambal River in Indi...

Gharial were historically distributed throughout the major channels of the Indus, Ganges, Mahanadi, Brahmaputra-Meghna and possibly Irrawaddy drainages, to elevations of <500 m, an estimated combined linear river distance of >20,000 km, or an historic occupancy area of 80,000 km² (using Red List standard 4 km² resolution). The species is currently...

Gharial Ecology Project Update 2018-2019

Gharial Ecology Project 2018 Annual Report

Reason(s) for Change in Red List Category from the Previous Assessment: Status is unchanged, but the criteria have been modified based on recent information by removing criterion C1 and adding criterion A2e. This species is the sole living representative of the family Gavialidae, which represents an ancient third lineage in the order Crocodylia (in...

Executive Summary An earlier field report (GEP 2017) established on a 425 km stretch of the National Chambal Sanctuary (NCS) from Pali to the Yamuna confluence, based on actual counts, the adult gharial population was 72 males with gharas (>4.5m), and at least 411 were reproductive females, based nest counts in 2017, immediately after hatching (GEP...

Abstract

Egg inundation often results in poor hatching success in crocodylians. However, how tolerant eggs are to submergence, and/or how eggshell ultrastructure may affect embryo survival when inundated, are not well understood. In this study, our objective was to determine if embryo survival in Caiman latirostris is affected by eggshell surface roughness,...

The Gharial (Gavialis gangeticus), endemic to the Indian subcontinent, has been classified as Critically Endangered by IUCN on the basis of a precipitous decline in distribution and abundance, as well as only a remnant global population (IUCN 2007). The National Chambal Sanctuary (NCS) in India holds the largest population of Gharial, estimated at...

Ambient temperatures during embryonic development determine gonadal sex in many reptiles. The temperature sensitive period for sex determination has been defined by shifting eggs between female- and male-producing temperatures in a few species. This phase spans 20-35% of embryogenesis in most species, which makes it difficult to define the mechanis...

This study followed the 2007-­‐08 mass mortality of gharial in the lower Chambal River, n. India. From 2008-­‐2015, 40 radio-­‐tagged gharials have been tracked during the monsoon and dry season annually, for 2+ yrs/animal. Individuals show different seasonal movements and residency patterns, dependent on size/age. Adult females move 80-­‐120 km po...

Abstract - The sex of American Alligator (Alligator mississippiensis) hatchlings is determined by the egg temperature during the middle third of the 9–12 week incubation period. As a consequence, predictable sex ratios are possible for clutches incubated in constant temperatures in the laboratory, but naturally occurring sex ratios of American Alli...

We examined agonistic behaviour in seven species of hatchling and juvenile crocodilians held in small groups (N = 4) under similar laboratory conditions. Agonistic interactions occurred in all seven species, typically involved two individuals, were short in duration (5-15 seconds), and occurred between 1600-2200 h in open water. The nature and exte...

Thesis (M. Sc.)--University of North Dakota, 1971. Includes bibliographical references (leaves 93-97). Microfiche (negative) of typescript.

The Gharial Ecology Project, also known as the Gharial Telemetry Project, was initiated in June 2008 to investigate the circumstances of the 2007-08 mass die-off of gharials in the 2- 4m size class, totaling 110+ individuals in the lower Chambal River. To date, 20 radiotagged gharials have been tracked successfully throughout the annual seasonal cy...

We examined agonistic behaviour in hatchling Australian freshwater crocodiles (Crocodylus johnstoni) at 2 weeks, 13 weeks, and 50 weeks after hatching, and between C. johnstoni and saltwater crocodiles (Crocodylus porosus) at 40–50 weeks of age. Among C. johnstoni, agonistic interactions (15–23 s duration) were well established by two weeks old and...

We assessed the ability of hatchling painted turtles (Chrysemys picta) from northern Minnesota to resist freezing when exposed to conditions like those occurring in natural hibernacula (natal nests). We placed animals individually into artificial hibernacula constructed in jars of damp, loamy sand and then lowered the temperature to approximately -...

Sex ratios of the American snapping turtle Chelydra serpentina are female-biased at cool temperatures, male-biased at moderate temperatures, and only females are produced at warm temperatures. The laboratory incubation of eggs at several constant temperatures yields patterns of skewed sex ratios. In this study, incubated eggs represented regional s...

Sexual differentiation of the gonads in Alligator mississippiensis and many other oviparous reptiles is controlled by egg incubation temperature. Estrogens are thought to play a role in this process, and it has been hypothesized that estrogen production is thermosensitive in species with temperature-dependent sex determination (TSD). Using the trit...

Although yolk steroids appear to play important roles in the development, growth, and behavior of some birds, their effects in oviparous reptiles are largely unknown. These investigations were initiated to determine initial levels of steroid hormones in the yolks of eggs from two turtle species. Clutches of snapping turtle (Chelydra serpentina) and...

Many oviparous reptiles exhibit temperature-dependent sex determination (TSD); i.e., the temperature at which the egg is incubated determines the sex of the offspring. In TSD reptiles, yolk steroids not only may influence sex determination, but also may mediate hormonal effects on subsequent growth and behavior, as in some avian species. We investi...

The formation of estrogens from androgens in all vertebrates is catalyzed by the "aromatase" complex, which consists of a membrane bound P(450) enzyme, P(450) aromatase (which binds the androgen substrate and inserts an oxygen into the molecule), and a flavoprotein (NADPH-cytochrome P450 reductase). Among vertebrates, the two major sites of aromata...

The formation of estrogens from androgens in all vertebrates is catalyzed by the “aromatase” complex, which consists of a membrane bound P450 enzyme, P450 aromatase (which binds the androgen substrate and inserts an oxygen into the molecule), and a flavoprotein (NADPH-cytochrome P450 reductase). Among vertebrates, the two major sites of aromatase e...

Recent theoretical papers on temperature-dependent sex determination in reptiles are based on the assumption that crocodilian populations, particularly adults, are markedly female biased. While there is evidence that some crocodile populations may conform to this expectation, there is no compelling evidence that American alligator populations are f...

The equilibrium freezing point for body fluids of hatchling Blanding's turtles (Emydoidea blandingii) is near -0.7 C, but neonates that are held in a dry, ice-free environment can be (super)cooled to approximately -6 C before they begin to freeze spontaneously (i.e., by heterogeneous nucleation). Unfrozen turtles recover from exposure to -4 C, so t...

Hatchling painted turtles (Chrysemys picta), Blanding's turtles (Emydoidea blandingi), slider turtles (Trachemys scripta), and snapping turtles (Chelydra serpentina) were inoculated with ice at temperatures near the equilibrium freezing point for their body fluids (ca. -0.7 C) and then frozen at -2.0 C. All animals survived freezing for up to 30 h,...

Temperature during embryonic development irreversibly determines gonadal sex in many oviparous reptiles. Although embryonic temperature also influences a number of other traits in these species. it is unclear whether such effects are primarily due to incubation temperature or to gonadal sex. Here we dissociated these normally confounding effects vi...

We assessed the ability of hatchling painted turtles (Chrysemys picta) from northern Minnesota to resist freezing when exposed to conditions like those occurring in natural hibernacula (natal nests). We placed animals individually into artificial hibernacula constructed in jars of damp, loamy sand and then lowered the temperature to approximately -...

Embryonic temperature influenced subsequent growth in juvenile snapping turtles, Chelydra serpentina: incubation temperatures of 24 and 26.5°C enhanced growth relative to a temperature of 29°C. Although embryonic temperature normally determines gonadal sex in this species, experimental manipulations revealed that temperature effects on growth were...

Unlike birds and mammals, in many reptiles the temperature experienced by a developing embryo deter mines its gonadal sex. To understand how temperature-dependent sex determination (TSD) evolves, we must first determine the nature of genetic variation for sex ratio. Here, we analyze among-family variation for sex ratio in three TSD species: the Ame...

Unlike birds and mammals, in many reptiles the temperature experienced by a developing embryo determines its gonadal sex. To understand how temperature-dependent sex determination (TSD) evolves, we must first determine the nature of genetic variation for sex ratio. Here, we analyze among-family variation for sex ratio in three TSD species: the Amer...

The leading explanation of temperature-dependent sex determination (TSD) in reptiles postulates that (1) ovarian differentiation is directed by estrogen and that (2) estrogen is synthesized in the developing gonad following induction of aromatase expression. However, the source of steroid substrate for aromatization has not yet been identified. In...

In many oviparous reptiles, incubation temperature determines hatchling sex. Manipulation of the embryonic hormonal environment can result in sex reversal. We measured circulating estradiol 17-β (E2) and testosterone (T) levels in temperature-determined and sex-reversed snapping turtles (Chelydra serpentina). Eight-month-old turtles have sex steroi...

We examined a critical component of the Charnov-Bull hypothesis of temperature-dependent sex determination (TSD) by determining the reaction norms of hatchling growth to embryonic incubation temperature in the common snapping turtle, Chelydra serpentina. Hormone manipulations of eggs produced females at male temperatures and vice versa, which there...

Incubation temperature determines sex in crocodilians and influences other features of hatchlings. We investigated the effects of incubation temperature, clutch, and sex on the dimensions, mass, and energy reserves of hatchling Alligator mississippiensis. Eggs from three clutches were incubated to pipping at constant temperatures of 29°, 31°, 32°,...

In certain reptiles with temperature-dependent sex determination (TSD), estrogens act as a signal for female differentiation. Because aromatase produces estrogens from androgens, this enzyme plays a pivotal role in TSD. Whether androgens act as the signal for male differentiation in TSD species in not yet clear. We manipulated the hormonal environm...

Genetic fingerprint profiles have been successfully used for establishing biological relationships, in linkage analysis, and in studies of population structure but have not so far been used for ascertaining phylogenetic relationships among related groups of species and genera. This is largely because these profiles are thought to evolve too rapidly...

Half of the 22 extant crocodilians show evidence of temperature-dependent sex determination (TSD). We examine evidence for TSD in 11 species by reviewing reports on five and presenting new data for six. The female-male pattern (FM; females at low temperature, males at high temperature) attributed to Alligator mississippiensis and Caiman crocodilus...

Individual-specific DNA fingerprints of crocodilians were obtained by the use of Bkm-2(8) probe. Pedigree analyses of Crocodylus palustris, C. porosus and Caiman crocodilus revealed that the multiple bands (22-23 bands with Aludigest) thus obtained were inherited stably in a Mendelian fashion. Unique fingerprints permitted us to identify individual...

Blood samples collected in the field for isolating DNA suitable for molecular analysis need special care in their storage and handling. In this article, we describe a simple method for the isolation of good-quality high-molecular-weight DNA that does not require low temperature conditions during collection, storage, and/or transportation of blood s...

We studied tolerance for cold in hatchling painted turtles (Chrysemys picta) from Lake Metigoshe, Bottineau County, North Dakota, to determine whether neonates in populations near the northern limit of distribution rely on a tolerance for freezing or on a capacity for supercooling to survive their first winter of life. We placed hatchlings individu...

Investigation of the reproductive biology and conservation of Crocodylus palustris provided the first documentation of a male crocodilian's excavating a nest and transporting hatchlings to the water without the assistance of a female parent. Male parental care in crocodilians varies in response to specific features of a species' organisation, matin...

1.1. The body temperatures (Tbs) and thermal behavior of hatchling New Guinea crocodiles (Crocodylus novaeguineae) were monitored in a terrestrial-aquatic thermal gradient exposed to the natural photoperiod.2.2. At 0–2 weeks of age, hatchlings selected of 33.4–33.9°C that were significantly elevated by 1.4–2.9°C above levels preferred subsequently....

The body temperatures ( T b) and thermal behavior of juvenile Alligator mississippiensis and Crocodylus acutus were monitored in an outdoor enclosure equipped with aquatic and terrestrial thermal gradients. Both species selected significantly higher and less variable T b s when fed than when fasted. Within each species, there were considerable indi...

We compare and contrast the signalling systems and social behaviors of Alligator mississippiensis, Crocodylus aculus, and Crocodylus mloticus. Our qualitative analysis focuses primarily on the behaviors of adults during three phases of reproduction: I. Defense of Territory and Courtship, II. Nesting and Incubation, and III. Hatching and Post Hatchi...

Juvenile American alligators in outdoor pens moved out of and into the water at sunrise and sunset, respectively. When the natural light cycle was extended with artificial illumination, these movements gradually shifted into phase with the altered light cycles; therefore, the amphibious behavior was modulated by a circadian rhythm cued by light. Mo...

Forty-sevn surface nests of the hispid cotton rat were observed in a grassy area bordering an airstrip on the Osa Peninsula, Costa Rica. Average nest dimensions were determined. Interior nest temperatures were significantly cooler than shade temperatures. Moderate precipitation was effectively excluded from nest interiors. Nests and nest entrances...

Understanding how Blanding's turtles utilize wetlands and uplands is crucial to protecting habitats critical to their conservation. The occurrence of Blanding's turtles in the Brainerd/Baxter area has been well established through the element occurrence records and from previous studies at Camp Ripley. During the course of this project, we captured...