3: Relict Leopard Frog - Status Part 3

What stochastic event occurred in Black Canyon, October 2006?

storm that caused debris flow

In 2017, what was the high-count of frogs?

1163

Monitoring - Relative Abundance: Visual Counter Survey Data (VES)

surveying the sight and taking the highest count

• minimum estimation of the total population of frogs

Estimate of' ‘True’ Abundance: Mark-Recapture

Catch, mark, and release a sample of animals

Then sample again, keeping track of those that are marked and unmarked (new captures)

The true abundace of the population can be estimated as…

X (total in population) / M (marked) = C (total captured in second sample) / R (recaptures)

Lincoln-Peterson Estimator

simplest of such estimates to estimate population size

What is the Double Sampling Method?

Conduct Mark-recapture and VES at the same site

The Double Sampling Method first calibrates relative abundance from…

VES to estimates of true abundance from Mark-recapture

Calibrating the relative abundance from VES to estimates of true abundance from Mark-recapture provides a ratio that you can then apply to:

VES data from other sites where there is no estimate of true abundanceE

Essentially, what does the Double Sampling Method provide?

a ratio or correction factor to adjust VES data

Change in total population over time:

Total population estimates

• Estimates for the entire species (post-metamorphs)

What do the total population estimates indicate?

Estimates of total populations increased over time from 2001 to 2017

Status of Translocation Site:

Grapevine Spring, AZ

Has rocky pools favored by frogs

Translocation Site:

Quail Spring, Spring 2008, after rehab effort → After cattle and burros abandoned the site in July 2010

no more open water, and no disturbances that hammered the vegetation

What are the translocation success criteria?

1. Over-wintering

2. Breeding Activity

3. Natural Recruitment

4. ‘Sustainable’ population

What is Over-wintering?

Do tadpoles/juveniles born in spring survive to next spring/survive winter

What is breeding activity?

Egg masses, tadpoles (born at sites)

What is Natural Recruitment?

Animals are born at the sight from animals that are at the sight

• Has to be documented

• often determined years after final release

What is ‘Sustainable’ population?

Is the population stable over-time?

Habitat management:

Mechanical vegetation reduction at Blue Point Spring

• maintain open habitat by reducing grass

Maintaining important breeding pools (habitat)

Most ‘volunteer’ crew maintaining important breeding pool in a drainage ditch along an access road in Hoover Dam

• frogs favor backwater habitat

In 2011, USFW Multidistrict Litigation:

USFWS legal agreement with WildEarth and Center for Biological Diversity to conduct actions under ESA for 251 candidate species including R. onca

What was the USFWS legal agreement with WildEarth and Center for Biological Diversity?

to conduct actions under ESA for 251 candidate species including R. onca

In 2016, Special Status Assessment (SSA) to inform listing decision on…

Updated:

• Current distribution

• Status of populations

• Current threats

• Mitigation needs (plans in terms of mitigation)

In 2016, just prior to the USFW decision, what was signed?

A revision and renewal of CAS

Current Stressors/’Threats’ Identified in 2016 SSA, revised CAS:

1. Present or threatened destruction or curtailment of habitat or range

2. Overutilization

3. Disease or predation

4. Inadequacy of regulatory mechanisms

5. Other natural or manmade factors affecting continued existence

6. Estimation of True Abundance

Why was overutilization negated as a ‘threat’/stressor?

There was no overutilization because all populations are on federal lands, illegal to use such frogs

Why was Inadequacy of regulatory mechanisms negated as a ‘threat’/stressor?

There were plenty of mechanisms to maintain populations

What did present or threatened destruction or curtailment of habitat or range involve?

1. Habitat degradation

2. Groundwater diversion and withdrawal

3. Overgrowth of emergent vegetation

4. Nonnative plants (invasive)

5. Burro and cattle grazing (but also a benefit)

6. Reduced connectivity of populations (but also a benefit)

Habitat degradation in Lake Mead:

drying out, underground water pressure decreasing, which led to no water rising up

How was burro and cattle grazing detrimental but also a benefit?

may hammer frogs, but also hammer vegetation, resulting in habitats that frogs favor

What did disease or predation involve?

• Nonnative crayfish, bullfrogs, fishes

• Amphibian chytrid pathogen

• Chytrid pathogen present within historical range and in one population in R. onca

• Negative impact on R. onca survivorship

What did other natural or manmade factors affecting continued existence involve?

• Small population size

• Flash, flood, events

• Drought and Wildfire

Evaluation of “stressor” severity (High, Medium, Low), conducted by USFWS

USFWS Listing Decision, 2016