Research Projects

Research Projects

Memphis Zoo scientists have contributed new knowledge and techniques to the field of conservation biology. Did you know that biologists can now freeze and then reanimate the sperm of many more species than in the past due to the work of Memphis Zoo scientists? Our breakthrough discoveries are the result of precise laboratory experimentation, applying the scientific method. All of our work, no matter how esoteric it might appear, is conducted with an eye toward gaining an important insight or tool which we then put to work to protect animals.

Overton Park Copperheads

Snakes in the City:

  • Animal: Southern copperhead, Agkistrodon contortrix contortrix
  • Project: To discern how the copperheads living isolated in Overton Park have adapted to their unusual situation.
  • Why?: As cities grow, we will need to better understand urban wildlife to preserve and manage habitat islands and the animals that live there. This research will provide an understanding of the behavior, ecology, and genetics of Overton Park copperheads. Malle Carrasco-Harris, a Ph.D. Candidate at the University of Memphis and Research Adjunct with the Zoo, records habitat preferences and life history traits, and compares genetic information with copperheads living elsewhere. Copperheads are an important part of the unique urban island of forest called Overton Park, and it is so important to unravel their interactions with the Park environment so we can insure they’ll always be a part of it.

Copperhead surgery to implant a radio-transmitter that allows for tracking of the wild snake. Snakes are held for a of couple days post-surgery for recovery before being released to the field. 

Assistant Curator Chris Baker with the largest copperhead found in Overton Park – 40 inches!  Chris is holding this magnificent snake while it is safely restrained in a tube.  

By tracking copperheads using radio-telemetry, many rarely seen behaviors have been documented, such as this pair in the act of breeding.  

Memphians enjoying Overton Park are often in very close proximity to copperheads, yet bites are almost unknown. Copperheads are shy and nonaggressive. 

Primitive Spider Ecology

Digging for Insights into Primitive Spiders:

Animal: Purseweb spiders and tropical tarantulas

Project: Determine how habitat destruction, alteration, pesticide toxicity, and fragmentation affect tarantulas and their relatives.

Why?: Since these spiders are long-lived (up to 20 years as opposed to 1-2 years for most spiders), extremely sedentary -i.e., they may live in the same burrow for years, and iteroparous (the technical term for reproducing multiple times during a lifetime as opposed to only once which is typical of most spiders) they are far more sensitive to environmental disturbances than other terrestrial invertebrates and thus potentially informative bio-indicators of an unhealthy environment – the proverbial “canary in the coal mine”.

Steve Reichling gathers data from tarantula burrows in Belize, including temperature, humidity, depth, the size and sex of the occupant, and microhabitat variables adjacent to the burrow.  

The entrance to the burrow of a large redrump tarantula in Guatemala.  That the burrow has an occupant is indicated by the veil of silk that the giant spider has spun across the opening, which helps maintain a stable temperature and humidity.  

This redrump tarantula is being released back into its burrow after being implanted with a passive-integrated transponder – the same device that’s used to “chip” dogs and cats – enabling researchers to identify it throughout its 15-20 year lifespan.  

Here, the underground portion of a purseweb spider’s silken tube is shown after being found in Overton Park’s Old Forest. 

Three purseweb spiders are set up in a field experiment to examine how microhabitat variables affect their life history. 

Many natural wonders in Overton Park’s Old Forest are easy to overlook.  The ethereal beauty of a purseweb structure can be easily damaged by a carelessly placed foot.  Please be careful and observant if you enter the Forest! 

Urban Avian Demographics

City Life: Forest Birds in the Greater Memphis Area

  • Animal: Eastern forest birds
  • Project: Many of our parks in the Greater Memphis Area hold the richest bottomland forest habitat in Shelby County. Some of these parks are completely isolated within the urban matrix, while others are connected to long corridors of habitat along associated waterways. Bird surveys are being conducted in four parks within Shelby County to look at differences in the bird assemblages in isolated versus connected patches of urban forest habitat.
  • Why?: Eastern songbirds have experienced precipitous declines in recent decades, largely because of habitat loss. Urban habitat patches can play an important role for wildlife, such as providing crucial stopover sites for migratory songbirds. The health of songbird populations can be used as a bioindicator of forest health, which can in turn influence regional habitat management strategies.

Bird surveys are taken at specific GPS points in the parks.

Barred owl observed through binoculars at a survey location.

Surveys are conducted in both winter and summer.

A pileated woodpecker forages in the winter near a survey point. 

Bird Banding Stations

A Bird in the Hand: Monitoring Mid-South Bird Populations

  • Animal: Eastern songbirds
  • Project: Strawberry Plain Audubon Center (Holly Springs, MS) is hosting a long-term bird banding station to document bird populations in their habitat preserve with the help of Memphis Zoo staff. Birds are netted, banded, and released, and a wealth of data are taken on each individual to document the demographics of various species and types of birds found in the forests and prairies of this region. Please visit this link for more information about this national program:
  • Why?: North American songbirds have experienced a precipitous decline in recent decades. Tracking detailed information over time for species in our region will help us understand which bird groups are under the greatest threat, from species to age class to nesting strategy. This information can help direct regional avian conservation resources to the bird populations most in peril. 

Jeff Hill (Memphis Zoo Bamboo Crew Member, far right) and colleagues remove birds from nets just after sunrise.

Kristina Mitchell (Independent Biologist and Master Bird Bander, right) processes a bird prior to its release with Fields Falcone (Memphis Zoo Conservation Lab Manager). 

A male orchard oriole just prior to release at the bird banding station. 

Wyoming Toad Hibernation

Hibernation to Help Future Generations

  • Animal: Wyoming toad (Anaxyrus baxteri)
  • Project: To determine if hibernation in captivity influences Wyoming toad sperm quality
  • Why?: Hibernation is a natural part of many animals’ lives, especially those that live in cold regions. Aside from helping animals survive the cold, hibernation also plays an important role in reproductive cycles. This poses a problem for animals, like the Wyoming toad, which live in captivity and don’t experience cold temperatures to cue hibernation. This study will help to improve captive breeding efforts in the Wyoming toad by zeroing in on the influence of hibernation and hibernation length on sperm quality to help ensure that breeding efforts are successful. 

A female Wyoming toad sits perched atop a rock at the Leadville National Fish Hatchery in Leadville, CO. Male and female toads can be easily distinguished by their throat coloration, with females having a light throat and males having a dark brown throat. 

Wyoming toads raised at the Leadville National Fish Hatchery in Leadville, CO are weighed and measured prior to being put in their “hibernation boxes.” These toads will go 1-2 months without food during hibernation, so it’s important to monitor their weight and size so that we can get an idea of how physically healthy the toads are before and after hibernation. 

Wyoming toads raised at the Leadville National Fish Hatchery in Leadville, CO are placed in plastic “hibernation boxes” to simulate a shortened winter in captivity. These boxes are outfitted with lots of holes for oxygen flow, moist moss, and carbon filter pads. To simulate cold weather, the boxes are placed in refrigerators set to 38o F. After a 1-2 month period, the toads are removed from the hibernation boxes and are ready to breed. 

Wyoming toads are collected around the Laramie Basin in Laramie, WY to assess the reproductive health of the wild population. The toads like to live in the grass surrounding the pond and can easily be found hopping around in the summer months. 

 Kristin Hinkson injects a male Wyoming toad with hormones to stimulate sperm production in hopes of assessing the reproductive health of the wild population. It takes around 4 hours for the hormones to take effect in these toads, so we place them in plastic boxes with water and wait!

Dusky Gopher Frog DNA Analysis

Guarding Against Inbreeding

  • Animal: Dusky gopher frog (Lithobates sevosus)
  • Project: To assess the genetic variation of both captive and wild dusky gopher frog populations
  • Why?: Genetic variation is important because it allows for species to better adapt and respond to changing environments (ex: a new disease outbreak or a degraded habitat). Genetic variation can easily be lost when population sizes are small, which is often the case for captive populations and endangered species, like the dusky gopher frog. Therefore, it is important to monitor genetic variation so that can we can not only ensure that captive populations are genetically representative of the wild, but also so that both the captive and the wild populations have enough genetic variation to avoid inbreeding. 

An adult dusky gopher frog is held by researchers prior to collecting genetic material for later DNA analysis. Genetic material can be collected in many different ways: through cheek swabs, skin swabs, or tissue collection. 

DNA can easily be extracted from dusky gopher frog eggs. Only one egg is needed per frog, and each female naturally lays hundreds of eggs. 

Tubes filled with dusky gopher frog eggs are placed in an orderly manner as a first step of DNA extraction. 

After DNA is extracted, the next step is to amplify a specific portion of the DNA that can give us clues about how much genetic variation is present. To do this, we use a process called polymerase chain reaction (PCR for short). This picture shows a 96-well plate where we can do 96 PCR reactions all at once!

DNA is amplified using this machine: a thermal cycler. This machine heats and cools the DNA to various sequences of temperatures—amplifying the DNA through a process called polymerase chain reaction.

Radiotracking the Dusky Gopher Frog

Tracking Captive-Raised Frogs Released into the Wild

  • Animal: Dusky gopher frog (Lithobates sevosus)
  • Project: The Memphis Zoo is leading a reintroduction program for the critically endangered dusky gopher frog by releasing captive-raised frogs into restored habitat. The goal of this project is to use radiotelemetry to follow frogs after they are released to evaluate their acclimation to the new environment.
  • Why?: By attaching miniature radiotransmitters to frogs and following them after they are released, we will learn about their survival, movements, and habitat preferences. This important information will help direct future conservation efforts for this species to save it from extinction.

Impacts of Invasive Cuban Treefrogs

Investigating Impacts of Invasive Frogs

Animal: Cuban treefrog (Osteopilus septentrionalis)

Project: The Cuban treefrog was accidentally introduced to the Florida Keys in the 1920s and has been spreading north since then. Through a series of experiments in the field and lab, in collaboration with colleagues at the University of South Florida and University of Florida, this project investigates how Cuban treefrogs are affecting native frogs and how they are adapting to life in Florida.

Why?: As the Cuban treefrog continues to spread, it is negatively affecting native frogs by competing with them and preying on them. This project will help us understand how this invasive species is impacting native species and ecosystems, how it is adapting to its introduced range, and where range expansion may occur in the future.

Increasing Tadpole Survival

Tadpole Bootcamp

  •  Animals: Fowler’s Toad (Anaxyrus fowleri)
  • Project: Finding ways to increase the chances that captive-bred tadpoles will survive in the wild by looking at their behavior and development.
  • Why?: When animals are raised in a captive environment, they sometimes have a hard time knowing what the appropriate behavior in the wild is. In their natural environment, they have no keepers to take care of them, no one to feed them, and the possibility that a predator will be lurking nearby. To help captive animals prepare for this big change, we are looking into ways of training animals to better adapt to their new environment.

Juvenile Fowler’s toad in the wild.

Juvenile Fowler’s toads in captivity.

Adult Fowler’s toad. 

Measuring Snake Hormones

Reproductive Ecology of Snakes

  • Animal: Eastern Indigo Snake (Drymarchon couperi)
  • Project: Determining hormone concentrations and the seasonal variation of hormones in fecals and skin sheds of captive Eastern indigo snakes in partnership with Central Florida Zoo’s Orianne Center for Indigo Conservation.
  • Why?: The measurement of hormones has been used extensively to monitor the reproductive, welfare, and physiological health in mammals. Yet, these methods have been less explored in reptiles. There is a need to better understand reproduction in reptiles to facilitate captive breeding efforts in zoos. Development of effective, non-invasive hormone monitoring techniques can provide insight into reproductive and stress physiology of endangered snake species and snake skin sheds may provide an alternative to fecal and plasma analysis.

Washing and drying bullsnake sheds to use for validation of hormone extraction methods.

Emily Lichtenberger, a Memphis Zoo research intern, grinding snake sheds and placing into tubes for hormone extraction.

Emily arranging ground tubes of sheds prior to adding solution for hormone extraction.

Pregnancy Detection

Are you pregnant?  

  • Animal: Snow Leopards (Panthera uncia) and Giant Pandas (Ailuropoda melanoleuca)
  • Project: Development of non-invasive pregnancy detection for snow leopards and giant pandas.
  • Why?: Pregnancy detection in captive carnivores is challenging because many species show similar changes in female physiology after mating whether the conception occurs or not. Also even captive wild animals are not easily handled for ultrasound or blood collection, making hands on detection methods difficult to use. The rapid urine tests used for humans do not work for most wildlife because these tests detect the presence of hormones that are unique to human pregnancy (and some non-human primates). However the testing of urine or fecal samples for pregnancy specific hormones and proteins offers an option for non-invasive preganancy testing in carnivores. Research scientisit Beth Roberts is working to validate pregnancy testing methods for giant pandas and snow leopards using urine and fecal samples and has determined pregnancy and predicted birth dates for animals at the Memphis Zoo and other institutions.

Pregnancy was successfully detected for snow leopard cub born at the Memphis Zoo in 2013, 30 days in advance of birth. Early detection of pregnancy allowed staff time to optimize husbandry for pregnancy and set up den and birthing areas.

Giant Panda Chemical Communication

Communicating, Giant Panda Style

  • Animal: Giant Panda (Ailuropoda melanoleuca)
  • Project: Identify pheromones produced by giant pandas that are related to sexual receptivity and mating behavior
  • Why?: Giant pandas are well known to display scent marking behaviors that are thought to advertise identity and sexual receptivity. However, it is unknown what chemicals are used by giant pandas and to what capacity these chemicals can be detected. Dr. Abbey Wilson at Mississippi State University conducted her doctoral research in collaboration with the Memphis Zoo in order to identify pheromones related to reproductive status, sexual motivation, and identity in both captive and wild giant panda populations. With low population numbers of giant pandas in the wild spread across fragmented habitats, a better knowledge of chemical communication in this species may provide vital information to improve the conservation and management of giant pandas.