In natural settings, adult fleas live for about a week. They can survive up to 185 days in artificial environments, or if their hosts are prevented from grooming.
Longevity in Artificial Conditions
Adult cat fleas can survive for months in laboratory settings. Maximum longevity was 86 days in one artificial system. In another, when fed human blood, their lifespans reached 139 to 185 days.
Fleas can live for long periods on hosts if grooming is restricted. In a 14 day experiment, 94.1% of female and 89.2% of male fleas survived. In another study, cats were declawed and fitted with collars to prevent grooming. After 50 days, 85% of female and 60% of male fleas were alive Fig 1. At 113 days, 76% of females and 50% of males were still living on the cats.
Fig 1 Percent of fleas surviving (y-axis) on 6 different cats (x-axis) after 50 days. The cats were restricted from grooming.
Grooming is the Primary Mortality Factor
In natural settings, nearly all fleas die from their host’s grooming activity. Unlike temporary parasites, such as mosquitoes, fleas permanently remain on their host after obtaining a blood meal. Thus, host grooming poses a major threat. On the upside, they’re are protected from harsh environmental conditions.
How Quickly Fleas are Removed
Cats kill over 50% of fleas living on them within a week, roughly 3-12 fleas a day. In one study, cats groomed off 19.5% of female and 38.5% of male fleas in a week Fig 2. Over 3 weeks, cats can remove 90% of their fleas. Generally, only 2-3% will survive for longer than this. In one 3 week experiment, cats removed 60% of male and 76% of female fleas. Some individual fleas may avoid removal. In one instance, a flea lived 9 weeks on a host.
Fig 2 Percent of fleas unaccounted for (y-axis) in four experiments lasting a week (x-axis) on the inter-host movement of fleas between hosts.
How the Fleas Die
The vast majority of fleas get ingested by the host during grooming. A small percentage may get dislodged. Dislodged fleas are often damaged during the process and will die in the environment. They’re commonly missing their heads or tarsi (bottom of legs). However, adult fleas have hard, resilient bodies. Some will survive. Undamaged fleas must return to the host within a couple of days or they’ll die of starvation.
Some Animals are Better Groomers than Others
Sensitivity to Fleas
Sensitivity to fleas differs among individual animals. Some groom themselves constantly, while others tolerate small to moderate numbers of fleas. The host’s ability to groom directly relates to the intensity of the infestation. Less efficient groomers are better hosts for fleas. Pets with flea allergies are meticulous groomers and will quickly reduce populations.
Fig 3 Mean percent of fleas removed (y-axis) by four different cats (x-axis) in a day.
Individual animals vary in their ability to remove fleas Fig 3. The grooming habits of four flea-infested cats were studied. The poorest groomer removed 4.1% of its flea population each day (22% per week). The fleas had a lifespan of around 18 days. The best groomer eliminated 17.6% of fleas per day (68% weekly), giving them an average lifespan of 5 days.
Young animals often have higher populations of fleas than mature animals. Juvenile cats have less experience with effective grooming techniques. Additionally, mature cats may have better immune systems, thicker skin, and changes in their blood capillaries.
Grooming is least effective in moderate flea infestations. In low levels of infestation, grooming off a small number of fleas has a significant impact on the entire population. In extreme infestations, fleas bites cause considerable irritation which triggers intense grooming.
Temperatures below freezing are lethal to adult fleas Fig 4. Emerged adults die within 5 days in subfreezing temperatures. Temperatures slightly above freezing kill them within 10 days. The lower limit for survival is 46.4°F (8°C), where 50% of fleas can survive for 20 days. Thus, they can’t survive outside in winter.
Fig 4 Percent of emerged adult fleas that survive (y-axis) across 40 days (x-axis).
Immature fleas are more vulnerable to the cold than adults. Eggs and larvae will fail to develop unless temperatures exceed 55.4°F (13°C).
Temperatures above 95°F (35°C) are lethal to adult fleas. Unless relative humidity is high, unfed fleas die within 2 days. Additionally, larvae die within their cocoons at 95°F. Outdoors, fleas can’t survive when temperatures exceed 95°F for more than 40 hours a month.
In household conditions, newly emerged fleas must feed within a week to prevent starvation Fig 5. They survive slightly longer in some experiments, but two weeks is the upper limit. 95% of fleas die within 15 days at 75.2°F (24°C) and 78% relative humidity. At 72.5°F (22.5°C) and 60% relative humidity, 95% die within 12.3 days.
Fig 5 Days it takes (y-axis) for 90% of newly-emerged, unfed adult fleas to die at various relative humidity percentages (x-axis).
Unfed fleas can survive significantly longer, up to 40 days, in humid environments with low temperatures Fig 5. In cool, saturated air, 62% of emerged adults will survive for 70 days. However, these conditions don’t occur in homes or outdoors during any season.
Host Removal & Malnutrition
Fleas feed immediately upon acquiring a host. Within a day, they double in weight and triple in protein. When removed from the host for 12 hours, they’ll lose all the gained weight and most of the protein. Beyond 12 hours of starvation, death is likely to occur from undernourishment. Fleas also become malnourished if they’re only able to feed for a few hours a day.
After feeding for a few days, fleas reach a point where they depend on a constant source of blood for survival. When removed from their host after 5 days of feeding, males die within 48 hours and females die within 96 hours. Off-host survival significantly increases (up to 14 days) if the initial feeding is restricted to 12 hours, because the threshold of dependency isn’t reached.
Time to Starvation
Typically, fleas die within 4 days of being removed from their host. When dislodged through grooming, male fleas die within 2 days and females within 3 days. Egg-producing females may starve in as little as 24 hours after host removal.
Females Live Longer
When isolated into compartments on a cat, female fleas live for an average of 11.2 days, and a maximum of 37 days. Males live for an average of 7.2 days, and a maximum of 25 days. Numerous studies show males having short lifespans than females. As a result, on-host flea populations consist largely of females.
Why Male Fleas Die Sooner
Both flea sexes have similar lifespans when unfed. Additionally, host grooming is equally effective in removing both genders, with neither being selectively reduced. However, males are more active on hosts. Females sometimes feed for up to 3 hours at a time, while males rarely remain attached for longer than 20 minutes. Increased mobility may explain the males’ shorter lives.
Extended Longevity of Pre-emerged Adults
After fully maturing, adult fleas can remain quiescent inside their cocoons while waiting for a host. Depending on ambient temperature, emergence can be delayed for up to 155 days. Metabolic activity is low in the quiescent state, which allows for the prolonged survival.
Once the fleas detect a nearby host, they’ll wake up and rapidly emerge from their cocoons. The primary factors which trigger emergence are warmth and pressure. A combination of both stimuli elicit the best response, as they indicate that an animal is resting on the cocoon. The pre-emerged state increases the likelihood of adults having access to blood meal immediately upon emerging, since they can’t survive long without a host.