Progress of the Anaxyrus houstonensis program
at Houston Zoo


Anaxyrus houstonensis

Common Name(s)

Houston Toad

Region where program is based

North America

Country where program is based

United States

The authority that recommended this species for an ex situ program

Amphibian Ark

Has a genetic analysis been performed on wild populations to define the target taxon, i.e., verify that single, viable Evolutionarily Significant Units (ESU's) that are managed as separate populations, are not confounded by cryptic species or polymorphisms?

If the answer to ESU is No, then there should be an entry for the needs in AArk's Conservation Projects list.

Name of the institution managing the ex situ population

Houston Zoo

Year the program started


Is at least some portion of the captive population maintained in range country?


Are sufficient resources available to manage the ex situ population?


If additional financial resources are required then there should be an entry for the needs in AArk's Conservation Projects list.

Are adequate numbers of skilled staff available with the appropriate ex situ amphibian experience?


Is sufficient space available for the required population size?


If additional facilities are required then there should be an entry for the needs in AArk's Conservation Projects list.

Has a Taxon Management Coordinator for the ex situ population been appointed?


Taxon Management Coordinator

Tyler Parker of Houston Zoo

Has a Taxon Management Group or Recovery Team been established?


Has a Taxon Management Plan, Recovery Plan or Species Action Statement been written?

In preparation

Web link to Taxon Management Plan

The most recent plan is not accessible on the internet at this stage.

Have Husbandry Guidelines been written?

In preparation

Have any knowledge gaps in the species biology or in their interaction with potential threats been identified that could benefit from research using the ex situ population?


List of knowledge gaps

There are some gaps in knowledge about the dietary/nutritional requirements of the species (and how that influences environmental carrying capacity in different forest types), about the interactions between the number of calling males and the hormone response of females (are there physiological thresholds?).

Have founder needs been calculated using the AArk Amphibian Population Management Guidelines ?


Have sufficient potential founders been collected? ( AArk Amphibian Population Management Guidelines recommends a minimum of 20 pairs of found animals).


Is the ex situ population managed by nationals from the range country?


What tools are used to maximize retention of genetic diversity?


Has the population produced viable offspring?


Have the first generation captive-bred animals bred successfully?


Is the ex situ population housed in permanent isolation from other populations occurring outside its range?


Is work being supported to study and mitigate threats to the species in the wild, either by the institution or by a regional wildlife agency?


Have captive-bred or captive-reared animals been released into the wild?


If releases were undertaken, have disease screening protocols or veterinary health checks been conducted prior to releases to the wild?


Is follow-up work being carried out to monitor progress of the released animals?


Is the taxon again secure in the wild, even if it might still require some ongoing in situ management? i.e. has the need for a captive assurance population been obviated such that we can call this a successfully terminated captive rescue program?



Genetic analysis has been performed and there are some differences between northern and southern sand bands (as many as nine "management units" were identified (McHenry and Fostner, 2009 Report to TPWD for Sec. 6 funding), for ex situ purposes we have defined 2 management units, north and south sand bands. Updated FWS Recovery Plan currently in review. Have released head-started animals. In 2015, the Houston Zoo bred 111 pairs of toads resulting in the release of ~600,000 eggs from 98 egg strands into native habitat in Bastrop County. Another 403 juvenile Houston toads were transferred to the Attwater’s Prairie Chicken National Wildlife Refuge to participate in a USFWS study examining the effects of habitat modification on Houston toad and prairie chicken populations.