Unexplained Animal Deaths at Lodi Lake

Wildlife
Written By Don Bradford
Wildlife Health Alert — Unexplained Animal Deaths at Lodi Lake
Wildlife Health Alert

Unexplained Animal Deaths at Lodi Lake

A Community Update from Friends of Lodi Lake • March 24, 2026

Official Update — City of Lodi Parks, Recreation & Cultural Services

Parks & Recreation and Animal Services are working with the California Department of Fish and Wildlife to determine the cause or causes of the animal deaths. Fish and Wildlife is actively investigating. As soon as more information is available, it will be shared with the public.

Summary

Over the past several weeks, park visitors and city staff have discovered deceased animals in and around the Lodi Lake Nature Area—including multiple deer, at least one fox, and waterfowl (ducks). None showed visible signs of injury, predation, or trauma. The City of Lodi Parks, Recreation & Cultural Services Department is actively investigating in coordination with state wildlife health agencies.

When multiple unrelated species die in a concentrated area and timeframe with no obvious cause, it warrants investigation. This is not a reason for alarm—it is a reason for awareness, caution, and careful reporting.

Historical note: This is not the first such event at Lodi Lake. In August 2015, at least five deer were found dead along the north trail under similar circumstances, prompting investigations by San Joaquin County Animal Services and CDFW. The cause was never publicly determined, and the deaths eventually stopped.

Possible Causes

Because the deaths span terrestrial mammals and waterfowl with no external injuries, investigators will focus on environmental toxins and diseases that cross species boundaries.

Likelihood Assessment by Cause Category

Investigator focus areas based on species affected and absence of external trauma

Environmental Toxins

Toxin

Cyanobacteria (Blue-Green Algae)

Lodi Lake is fed by the Mokelumne River and surrounded by agricultural land, making it susceptible to harmful algal blooms (HABs) as temperatures warm in spring. Cyanotoxins are lethal to all mammals and birds that drink contaminated water, causing sudden death with no external injuries. Watch for: green or blue-green scum, unusual water discoloration, foul or musty odors.

Toxin

Anticoagulant Rodenticides (Rat Poison)

Second-generation anticoagulants are detected in roughly 95% of mountain lions, 83% of bald eagles, and numerous foxes, bobcats, and deer tested statewide. These poisons cause fatal internal bleeding with no visible wounds. Rodenticide bait placed near the park or surrounding properties can enter the food chain through poisoned rodents, affecting multiple species.

Toxin

Agricultural Chemicals

The Lodi area is one of California’s premier wine grape regions. Pesticide or herbicide runoff into the Mokelumne River watershed could introduce toxins harmful to wildlife drinking from or foraging near the lake.

Disease

H5N1 Highly Pathogenic Avian Influenza

An urgent concern right now. H5N1 is actively circulating in California. As of February–March 2026, it has crossed into marine mammals at Año Nuevo State Park and was suspected in dozens of dead Canada geese in Stockton—just 13 miles from Lodi—in early 2026. The virus can spill over to mammals that scavenge infected birds.

Disease

Leptospirosis & Tularemia

Both are waterborne bacterial infections capable of affecting deer and foxes. They cause organ failure and death without external symptoms and are transmitted through contaminated water, ticks, or direct contact.

Waterfowl

Avian Botulism

The most common cause of mass waterfowl die-offs in California’s Central Valley. Caused by Clostridium botulinum bacteria that thrive in warm, shallow, stagnant water. The toxin paralyzes birds, which drown or die from respiratory failure—leaving no external injuries. Avian botulism killed over 75,000 birds at Tule Lake National Wildlife Refuge in 2024.

Waterfowl

Avian Cholera

A rapidly spreading bacterial disease (Pasteurella multocida) that kills waterfowl suddenly through direct contact and contaminated water. More common in winter and early spring. Major California outbreaks have killed thousands of birds at the Salton Sea, Clear Lake, and Klamath Basin.

Most Likely Scenario

The most compelling single explanation for deaths across deer, fox, and ducks is cyanotoxin poisoning from a harmful algal bloom—all species drinking from the same contaminated water source. It’s also possible two concurrent events are occurring: an avian disease (botulism, cholera, or H5N1) affecting waterfowl alongside a separate environmental toxin (cyanobacteria or rodenticides) affecting mammals. Investigation will clarify this.

What Happens Next

Wildlife mortality investigations take time. The typical timeline:

  • Days Field investigation — Agencies document the scene, collect specimens, and assess environmental conditions.
  • Days–Weeks Necropsy — Pathologists examine internal organs and tissues for disease, trauma, or poisoning.
  • Weeks–Months Laboratory testing for specific pathogens, toxins, or contaminants.
  • Weeks–Months Results analysis, reporting, and any public health recommendations.

CDFW typically issues public updates when significant findings emerge or when there are public health implications. Friends of Lodi Lake will share updates as they become available through our website, Facebook, and Instagram (@friendsoflodilake).

Visitor & Pet Safety Guidance

Until the cause is determined, we recommend the following precautions:

For Visitors

  • Stay on designated trails and avoid areas where dead animals have been found.
  • Do not touch, move, or handle any dead or sick wildlife—even with gloves. Photograph and report from a safe distance.
  • Avoid contact with the water until water quality has been confirmed safe. Do not allow children to play in or near the lake.
  • Wash hands thoroughly after visiting the park, especially before eating.

For Pet Owners

Dogs are highly susceptible to cyanotoxins, avian influenza, and rodenticides.

  • Keep dogs on leash at all times.
  • Do not allow dogs to drink from or swim in the lake, or approach dead animals or waterfowl.
  • Watch for signs of illness: vomiting, lethargy, seizures, difficulty breathing, or unusual bleeding.
  • Contact your veterinarian immediately if your pet shows symptoms after visiting—mention the wildlife mortality situation.

Do Not Feed Wildlife or Feral Cats at Lodi Lake & the Nature Area

Feeding wildlife and feral cats is harmful under any circumstances — but during an active wildlife health investigation, it can actively spread disease and interfere with the investigation. Please do not feed any animals at Lodi Lake or the Nature Area.

  • Waterfowl & birds: Bread, crackers, chips, and human food are nutritionally harmful to ducks and other waterfowl. Feeding concentrates birds in small areas, accelerating transmission of avian diseases like botulism, avian cholera, and H5N1. It also causes ducks to congregate near paths, increasing human exposure risk.
  • Deer & mammals: Supplemental feeding attracts deer to human areas, stresses their digestive systems, and increases contact between individuals — which is exactly how diseases like leptospirosis, tularemia, and CWD spread within a population.
  • Feral cats: Feral cat colonies fed by well-meaning visitors are a documented pathway for disease transmission between domestic and wild animal populations. Cats prey on the same birds and small mammals currently under investigation and can carry and spread diseases across species. Feeding programs sustain colonies that would otherwise be managed by animal services.

Feeding wildlife is prohibited under California Fish & Game Code §4150 and Lodi Municipal Code. If you see someone feeding wildlife or maintaining feral cat feeding stations in the park, please report it to City of Lodi Parks & Recreation at (209) 369-0404 or San Joaquin County Animal Services at (209) 953-6073.

What to Watch For and How to Report

Community observations are often the first signal that triggers official investigation. If you visit Lodi Lake, watch for:

Algal Blooms

Green, blue-green, or brown scum; unusual water color or odor; foam or organic mats on the surface.

Sick or Disoriented Animals

Birds unable to fly or walk; mammals stumbling or lethargic; tremors, seizures, or circling behavior.

Dead Animals

Any fresh carcasses, especially multiple animals in the same area or near water. Do not move or bury carcasses—this destroys evidence.

How to Report

  • CDFW Online Mortality Report wildlife.ca.gov → Wildlife Health → Mortality Report — Accepts GPS location, photos, species description, and environmental observations. Feeds directly to CDFW’s Wildlife Health Lab.
  • CalTIP Hotline (24/7, anonymous) Call 1-888-334-2258, text “CALTIP” + your message to 847411, or use the free smartphone app. Ideal for suspected poisoning, pollution, or wildlife crimes.
  • CDFW Wildlife Health Lab (916) 358-2790 | WILab@wildlife.ca.gov
  • CDFA Sick Bird Hotline 1-866-922-2473 (suspected avian influenza)
  • City of Lodi Parks & Recreation (209) 369-0404
  • San Joaquin County Animal Services (209) 953-6073
  • Friends of Lodi Lake friendsoflodilake.org or our Facebook page

When Reporting, Note:

  • GPS location or landmark
  • Number of animals and species (if known)
  • Water conditions, odors, or visible algae
  • Any recent environmental activity nearby (construction, spraying, runoff)

Agencies Involved

Several agencies share jurisdiction over this situation. Coordination among them ensures a thorough investigation and appropriate public health response.

Agency Role & Contact
City of Lodi Parks, Recreation & Cultural Services Park management; initial response; coordinates with state agencies. (209) 369-0404
CA Dept. of Fish and Wildlife — Wildlife Health Lab Lead agency for wildlife investigations; conducts necropsies and toxicology testing. (916) 358-2790 | WILab@wildlife.ca.gov
San Joaquin County Animal Services Responds to mortality calls; removes deceased animals. (209) 953-6073
San Joaquin County Environmental Health Investigates environmental contamination and water quality concerns.
Central Valley Regional Water Quality Control Board Monitors Mokelumne River and Lodi Lake water quality.
CA Dept. of Pesticide Regulation Investigates suspected pesticide-related wildlife kills.
CA Dept. of Food & Agriculture (CDFA) Coordinates avian influenza investigations. Sick Bird Hotline: 1-866-922-2473

What Friends of Lodi Lake Is Doing

As a community organization dedicated to Lodi Lake since 1986, we are actively engaged in this situation:

  • Staying in contact with city staff and investigating agencies and sharing updates as they become available
  • Advocating for thorough investigation, including water quality testing and necropsy/toxicology analysis
  • Coordinating with volunteer docents who regularly walk the Nature Trail to report additional findings

We encourage community members who love Lodi Lake to stay informed, stay cautious, and report anything unusual. Lodi Lake’s 58 acres support over 100 bird species and dozens of mammals, reptiles, and amphibians. California has weathered far larger mortality events—75,000 birds at Tule Lake in 2024, thousands of marine mammals from toxic algal blooms in 2025—and populations have recovered. The system works when the public and agencies work together.

Key Takeaways

  • Multiple-species deaths with no visible trauma merit investigation but are not cause for alarm.
  • Do not touch dead or sick wildlife. Photograph and report from a safe distance.
  • Do not feed wildlife. Prohibited by State Law and City of Lodi Ordinace.
  • Keep pets on leash and away from the water and any dead animals.
  • Watch for algal blooms, water discoloration, and unusual animal behavior.
  • Report observations through CDFW, CalTIP, local agencies, or Friends of Lodi Lake.
  • Investigations are underway—results may take weeks to months, but California has robust wildlife health systems.

Stay Connected with Friends of Lodi Lake

friendsoflodilake.org • facebook.com/Friends-of-Lodi-Lake • @friendsoflodilake

This document will be updated as information from investigating agencies becomes available.

References & Reporting Links

Don Bradford
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