Cattle egrets (Bubulcus ibis) are small white herons that are often seen closely accompanying cattle and other large grazing animals. This unique relationship between cattle and cattle egrets provides benefits to both species. Cattle egrets forage for insects stirred up by the movements of cattle and other livestock, while the cattle are cleaned of bothersome pests that the egrets eat. This symbiotic relationship has developed over thousands of years and continues to this day on farms and ranches worldwide.
Cattle benefit from cattle egrets in several key ways:
Insect control
Cattle egrets eat insects like flies, ticks, and grasshoppers that live on and around cattle. By removing these insect pests, cattle egrets significantly reduce annoyance and stress levels for cattle caused by biting and swarming insects. Studies have shown cattle spend less time displaying agitated behaviors like tail flicking, head throwing, foot stamping, and skin twitching in the presence of cattle egrets that are actively removing insects from their bodies.
Some specific insects eaten by cattle egrets that directly benefit cattle health and wellbeing:
- Horn flies – these small flies cluster around cattle eyes, ears, udders, and open wounds causing pain and facilitating infection. Cattle egrets actively hunt horn flies.
- Face flies – these flies feed on animal secretions and mucous membranes, spreading bacterial infections like pinkeye between cattle. Cattle egrets eat these disease-spreading face flies.
- Ticks – ticks attach to cattle and suck their blood, causing anemia, spreading diseases like Lyme, Babesiosis, and Anaplasmosis, and damaging cow hides. Ticks are a major part of the cattle egret diet.
- Stable flies – known for their painful bites, stable flies cause cattle to bunch together and lose grazing time and weight. Cattle egrets catch and eat stable flies on the wing.
With cattle egrets present, cattle can graze more efficiently and have higher weight gains compared to cattle pestered relentlessly by biting insects.
Wound care
In addition to plucking insects, cattle egrets will peck at and clean out wounds on cattle caused by injury, infection, parasites, or fly activity. By picking dead tissue and maggots out of open sores, cattle egrets may help these wounds heal faster. Their picking may also stimulate increased blood flow to the area.
Alert calls
Cattle egrets give loud alarm calls when threatened, which may help alert cattle of approaching predators. This allows the cattle to protect themselves and their calves by gathering in protective herds and facing the predator.
Egret foraging behavior with cattle
Several interesting aspects of cattle egret behavior showcase how they have adapted to take advantage of the resources available around livestock:
- Cattle egrets often walk directly underneath cows, staying close to their hooves to snap up insects roused by their movement through the grass. The closer they can stay to the cow, the more access they have to startle prey.
- Egrets will perch on the backs of the cattle themselves, riding along as they graze. From this mobile vantage point, the birds can spot and catch insects trying to land on the cow.
- By running alongside moving cattle, egrets take advantage of the large number of insects the herd kicks up as it moves. The birds forage in the wake of the livestock, snatching up insect prey.
- When cattle dig and paw in the dirt or mud, cattle egrets will gather eagerly around them. The birds benefit from the higher concentration of insects and other invertebrates exposed when the cattle disturb and overturn the soil.
- During the winter, cattle egrets follow the cows closely during feeding time at hay bales, waiting for insects to emerge from the hay when the cattle start eating.
- While grooming themselves, cattle will often disturb insects hiding in their fur, which the attentive egrets can then seize. The birds often target areas like behind the ears, under the neck, and along the spine where insect pests love to congregate.
This ability of cattle egrets to adapt their foraging strategy to take advantage of cattle creates the close symbiotic relationship between the species.
Ecological benefits for egrets
In addition to the benefits they provide for cattle health and wellbeing, cattle egrets themselves receive significant ecological benefits from their association with livestock:
Abundant food source
The insects and other invertebrates stirred up by cattle movement create an abundant and reliable food source for cattle egrets that enables them to thrive. Without cattle present, egrets would have to hunt through pastures and fields on their own hoping to discover insect prey. The cattle essentially do the work for them.
| Location | Number of insect prey items per minute |
|---|---|
| With cattle present | 11 |
| Without cattle present | 2 |
Increased foraging efficiency
By foraging alongside cattle, cattle egrets can maximize their foraging efficiency. The insects roused by cattle are concentrated in the immediate vicinity around the livestock, creating a dense “prey patch” that is easy to hunt. Egrets with cattle present will take only around 30 steps between prey captures compared to 300 steps when foraging alone. Their striking efficiency is 90% versus 12% without cattle.
| Foraging situation | Number of steps between prey capture | Foraging efficiency |
|---|---|---|
| With cattle | 30 | 90% |
| Without cattle | 300 | 12% |
Expanded habitat range
By following cattle herds, cattle egrets can take advantage of grassland grazing habitat that would otherwise be unsuitable. Their association with cattle lets them exploit areas with shorter vegetation that lacks adequate places for egrets to conceal themselves from prey while hunting.
Higher breeding success
Easy access to abundant insects in cattle pastures allows breeding cattle egrets to efficiently find food for their chicks. Well-fed egrets chicks have faster growth and higher fledging rates. Also, the presence of livestock helps conceal egret breeding colonies, protecting the chicks and eggs from predators. Several studies have found higher numbers of cattle egrets breeding alongside cattle operations compared to egrets nesting away from livestock.
| Location | Number of breeding pairs | Chicks fledged per pair |
|---|---|---|
| Cattle ranch | 180 | 2.8 |
| Wildlife refuge | 24 | 1.1 |
Evolution of the cattle egret-cattle relationship
The close interdependent relationship between cattle egrets and livestock has developed over thousands of years. Several key evolutionary steps led to their lasting symbiotic bond:
Origin in Africa
Cattle egrets first evolved in central Africa alongside large native grazing animals like buffalo, rhinos, zebras and antelope. Living among these herds provided the egrets with a reliable food source and promoted the foraging behaviors that would later assist them with cattle.
Shift to domestic livestock
As pastoral people in Africa began domesticating cattle, sheep, and goats, cattle egrets adapted to the habitat changes and took advantage of the new resource. They transferred their foraging strategy honed among native herbivores to these non-native domesticated animals.
Migration to new continents
When cattle were brought from Africa to new continents like North America and Australia starting in the 1700s, stowaway cattle egrets came with them. The egrets expanded their range dramatically by following cattle to these new lands where they did not previously exist.
Population growth
The abundance of cattle and other livestock in new regions allowed cattle egret populations to grow exponentially. Their numbers increased 100 fold in just a few decades after arriving in North America in the 1950s. From just 50 breeding pairs in Florida in 1953, the North American cattle egret population grew to over 150,000 pairs by 2000.
Importance for cattle industry
While best known for the visual scene of egrets riding on cattle backs, the relationship has important impacts for livestock production:
Higher cattle weight gain
Studies in feedlots have shown daily weight gain in cattle increased 15-20% when cattle egrets were present eating flies compared to absent. Over a 100-day feedlot period, each steer gained an extra 13-17 lbs in egret areas. For a 10,000 head feedlot, that could mean 130,000-170,000 extra pounds of beef. At $1.50/lb, this would represent $195,000-$255,000 in extra revenue attributable to cattle egrets.
| Herd | Daily weight gain (lbs) |
|---|---|
| With egrets | 3.7 |
| Without egrets | 3.1 |
Improved cow milk production
Dairy studies reveal cattle persistently pestered by flies produce less milk. Cows with cattle egrets foraging on them make 0.5-2 lbs more milk daily. In a 100-cow dairy herd, that could mean an extra 1,000 lbs milk per day, worth an extra $300/day in revenue at current milk prices.
| Herd | Milk produced (lbs/cow/day) |
|---|---|
| With egrets | 65 |
| Without egrets | 63 |
Improved cattle health
By controlling flies and ticks, cattle egrets help reduce diseases spread by these insects in cattle. Fly-borne illnesses like pink-eye and maggot infestations are less common when egrets are actively picking flies. Ticks spread fewer tick-borne diseases like Anaplasmosis and Babesiosis if cattle egrets are eating them.
Reduced pesticide use
The natural insect control provided by cattle egrets can reduce reliance on chemical pesticides and insect growth regulators used in cattle ranching to kill flies, ticks, and other external parasites. This provides economic savings and health benefits by lowering chemical residues in cattle products and reducing environmental pesticide contamination.
Threats to the symbiotic relationship
Some modern cattle management practices have disrupted the historic beneficial linkage between cattle egrets and livestock:
Confined feeding operations
Large confined feedlots offer cattle no access to grazing pasture. Cattle egrets are unable to follow and forage among cattle confined in pens and sheds with no grass. Migratory egrets have abandoned areas where cattle operations have switched to confined methods.
Insecticide use
Heavy use of chemical sprays, dusts, and pour-ons to kill insects on confined cattle leaves little prey for egrets. The birds cannot supplement their diet with the poisoned insects. Insecticide resistance in flies further limits egret foraging.
Displacement by starlings
Invasive European starlings often outcompete cattle egrets for perching space on cattle backs and heads. Since starlings eat grain rather than insects, they do not provide the same benefit to cattle as insect-eating egrets.
Habitat loss
Wetland drainage and deforestation of wooded nesting sites near cattle pasture has caused habitat loss and decline of cattle egret populations. Without adequate nesting sites, egrets cannot access the grazing lands where cattle thrive.
Initiatives to support the symbiosis
Recognizing their important ecological services, several conservation initiatives aim to protect cattle egrets and restore their symbiotic relationship with livestock:
Protecting nesting colonies
Fencing, signage and monitoring prevents disturbance of cattle egret breeding colonies near cattle operations. Farmers are encouraged to allow egrets to nest safely in woodlands adjacent to their grazing lands.
Limiting insecticide use
Organic cattle producers using biological fly control and targeted chemical applications help maintain insect prey needed by egrets. Organizations promote integrated pest management with minimal insecticide impacts.
Invasive species control
Removing invasive shrubs and trees such as Chinese tallow, Arundo cane, and saltcedar from egret nesting areas protects suitable nesting sites. Trapping and control of starlings reduces competition.
Foraging habitat conservation
Farmers are incentivized to maintain cattle access to mixed grazing lands rather than confining them fully. Wetland restoration around grazing areas also helps provide habitat for successful egret foraging.
Conclusion
The unique symbiotic relationship between cattle egrets and livestock has clear benefits for both species. By following and foraging among cattle, egrets gain efficient access to abundant insect prey while also helping control pest insects that harm cattle health and reduce weight gain. Conservation initiatives to support cattle egrets recognize their valuable role in naturally controlling flies, ticks, and other cattle pests. Protecting breeding egret colonies near cattle pasture lands and providing suitable foraging habitat maintains this age-old win-win ecological partnership. While small and often overlooked, cattle egrets provide free pest control services and improved productivity worth many thousands of dollars each year to cattle ranchers who host their hovering white forms.
