Rapid DNA Testing for Poisonous Plants

When Wildlife Eat Poisonous Plants: What to Watch For & How Rapid DNA Testing Can Help

Imagine a small group of endangered rhinos has just been reintroduced to a protected valley. The release plan looks perfect on paper: good grass cover, reliable water, minimal risk of poaching or other human disturbances. Then, within days, several animals begin showing classic gut-pain behaviors: repeatedly lying down and getting back up, pawing at the ground, rolling around. A field team notices profuse salivation in one animal and diarrhea in another.

Now the clock is running. In animals like rhinos, with large ‘hindgut fermenting’ digestive systems, the effects of plant toxins can move from subtle to catastrophic quickly. To save these animals, to make sure others don’t get sick, and to protect the future of the rewilding initiative we can’t take a risk in guessing what kind of treatment might work—we have to quickly figure out what, exactly, they have been eating. That’s where any preparation to enable rapid dietary testing can help guide our response in real time.

Emerging strategies that enable rapid DNA testing to minimize the economically costly loss of livestock are becoming highly effective and scalable—they are about to spill over into the wildlife sector where they can help bolster conservation initiatives as well. We anticipate this could become especially important for wildlife translocation and reintroduction programs, where animals are presented an array of unfamiliar foods that their systems are not accustomed to. 

Red Flags: Signs of Plant Poisoning Can Be Easy to Miss

Wildlife poisonings are under-detected because sick animals may hide, get taken by predators, or die and decompose before they are detected. When you do detect cases of plant poisoning, they typically look like abrupt changes in the ways animals behave or their  or survival.
​
Common signs of poisoning in different types of animals

• Neurologic & behavioral: staggering, tremors, weakness, unusual aggression or dullness, head pressing, pacing in circles, collapsing, seizures.
• Gastrointestinal: sudden losses of appetite, drooling, diarrhea, dehydration.
• Respiratory & cardiac: labored breathing, sudden collapse, sudden death.
• Liver: poor body condition, jaundice, photosensitivity such as lesions on skin.
• Reproductive: miscarriages, neonatal failure to thrive, congenital defects.

Differences in digestive systems matter

• Hindgut fermenters (rhinos, zebras, many lagomorphs): animals like these often exhibit toxic irritation, dysbiosis, or impaired movements that often appear in the form of colic, ileus, reduced fecal output, depression, or shock.
• Ruminants (wild ungulates, cattle, sheep, goats): some toxicoses show up early in the form of rumen dysfunctions like bloat or reduced cud-chewing before more systemic signs appear.

A key thing to notice is if multiple animals start to show similar signs within a short window after a release or translocation, as this can be an indicator that dietary changes or other environmental exposures are causing the problem.

Poisonous Plant Hazards for Wildlife Managers

Globally, the most relevant plants for management fall into three categories. The first is the highly lethal plants, for which even small amounts of exposure can matter. The second includes those that bear chronic toxins, which can erode an animal's overall health and reproductive capacity over time. The third covers "conditional hazards" that become dangerous only under certain conditions such a weather, disturbance, or land-use impacts.

I'll provide several examples from the American West, where rangeland toxicosis has been exceptionally well-studied—and where we have learned to recognize patterns that are widely transferrable.

1. Fast-acting, high-lethality plants: small doses can be fatal

• Water hemlock (Cicuta spp.): among the most dangerous plants that can cause rapid seizures and sudden death.
• Poison hemlock (Conium maculatum): neurologic weakness, respiratory failure, and developmental defects.
• Yew (Taxus spp.): tremors, weakness, heart and respiratory failure.
• Oleander (Nerium oleander): globally relevant ornamental with potent cardiac glycosides; risk increases near towns and where clippings are dumped.
  
• Death camas (Toxicoscordion spp., Zigadenus spp.): cardiac effect risks spike in spring when leaves are especially toxic and desirable forage is sparse.
• Larkspur (Delphinium spp.): a major concern on rangelands across the America West as it can cause neuromuscular weakness and sudden death.

2. Chronic "slow-burn" toxins: population-level impacts on survival and reproduction 

• Ragwort/groundsel (Senecio spp., Jacobaea spp.): irreversible liver failure often appears months after exposure.
  
• Fiddleneck (Amsinckia spp.): severe liver fibrosis and "walking disease." 
  
• Houndstongue (Cynoglossum spp.): weight loss, jaundice, photosensitization, liver failure
• Locoweed (Astragalus spp., Oxytropis spp.): chronic neurologic and reproductive effects arise as animals may continue eating it over weeks after becoming habituated to it.
• Lupines (Lupinus spp.): neurologic issues and congenital defects when mothers eat it during sensitive gestational windows.

These kinds of chronic toxins can be hard to link to one exposure event, and they are easy to miss until animals show health declines or photosensitivity.

3. Situation-dependent "conditional hazards": risk spikes depending on environment

• Nitrate accumulators: species varies by region, potentially causing methemoglobinemia and hypoxia.
• Cyanogenic (prussic acid) producers: some forage types and wild relatives increase production after frost or plant stress.
• Photosensitizers: some plants cause this effect directly (primary) while others do so indirectly via chronic liver damage (secondary), reducing health and survival especially in sun-exposed habitats.
  

Why Wildlife May Tolerate (Some) Plants That Harm Livestock

A common trap in mixed-use landscapes is assuming that a plant is safe to eat just because local wildlife can be seen eating it. Sometimes wildlife tolerate plants better—sometimes not--making it hard to generalize from one species to another.

Sometimes wildlife are able to "get away with" eating toxic plants. The reasons can vary broadly, and many can apply to the same situation:

• Co-evolution & local adaptation: exposure through the generations can select for greater tolerance or behaviors to manage exposure (e.g., eating clay).
• Detox strategies: liver enzymes, gut microbiomes, and absorption rates vary by species and can depend on factors that determine basal metabolic rates such as body-size .
• Doses & diet-mixing: wildlife often nibble on small amounts of many plant species over the course of a single day, thereby avoiding the threshold for toxic effects.
• Selectivity & timing: animals may select the least toxic plants or plant parts available, or avoid feeding on certain plants at times or places where the toxins tend to be most concentrated.

​Of course, wildlife are not immune to toxins. Highly toxic plants, concentrated exposures, and novel conditions can still still overwhelm their systems and harm populations.

Management Strategies Can Make Livestock More Vulnerable 

Even when wildlife and livestock forage under otherwise identical conditions, their risk profiles can differ. Management strategies make a difference in how exposure occurs.

Compared to wildlife, livestock often get bigger meals with less choice. They are bred and conditioned to grow quickly, and therefore may take larger bites, feed more continuously, and be held in smaller areas that limit choice. Likewise, overgrazing can create conditions that favor toxic plants that are initially avoided but become unavoidable—at the same time as animals have less opportunity to engage in diet-mixing or other behavioral strategies to ameliorate the effect. Finally, toxic plants can be baled into hay or contaminate feed in ways that cause repeated exposure, which can be especially relevant for chronic liver toxins that cause effects over time.

How DNA-based Diagnostics Can Make the Difference

The most effective prevention and response strategies involve coordination among universities, veterinarians, plant taxonomists and herbaria, extension and range specialists, and wildlife health agencies.

Rapid DNA testing of animal diets provide a novel source of information that is increasingly viewed as a force multiplier. These types of tests are not intended to reveal 'the truth' about what animals eat or what might make them sick on their own, but they provide highly clear data that can be difficult or impossible to get in any other way. And the information arrives at ever-increasing speeds—bolstering our ability to make good decisions at the pace required for management.

Using dietary DNA, diagnostic testing can allow for faster and more targeted treatment. When we can confirm--or at least identify a strong suspect—veterinarians can provide better care and field agents can identify which animals or habitats require intervention. For example, we can take immediate steps to fence off an infested field, move animals, provide supplemental feeding, or remove specific plants without requiring the use of broad-scale herbicides or expensive habitat modifications.

In all of these ways, understanding the potentially toxic effects of plants on wildlife and livestock can improve the success of planned reintroductions and translocations while reducing the costs associated with common points of failure.

Be Ready Before A Crisis Hits: How To Prepare & Get Started

The scenarios we considered here—a rhino showing colic signs days after release, livestock declining mysteriously through a grazing season, co-occurring species responding differently to their shared food base—all point to situations where we might have an opportunity to improve conservation outcomes if we prepare before animals get sick.

Anyone involved with rewilding programs, translocations, or rangeland management carries the responsibility to avoid animal poisoning and respond quickly when it is suspected. That means conducting vegetation surveys and establishing plant collection protocols for target sites before the animals arrive and monitoring how the flora changes as the animals become habituated. While emerging diagnostic technologies such as dietary DNA metabarcoding can provide rapid results, learning and preparing to use the technology to its full potential can require preparation. 

We recommend learning how to build or contribute to a plant DNA reference library that reflects your regional flora, and training field teams to collect plant and dietary samples for the lab. Even if there is not an immediate concern, banking these kinds of samples can provide critical comparative information when the time comes.

If you are planning a translocation, please consider reaching out to us at the Genomic Opportunities Lab. We collaborate with programs like the USDA's Poisonous Plant Research Lab to develop and deploy rapid DNA-testing technologies that help with livestock poisoning in the western United States—we may be able to provide general guidance or contract with you to ensure your conservation programs succeed as well.