Wild guppies generally feed on a variety of food sources, including benthic algae and aquatic insect larvae.

It was named Girardinus guppii by Albert Günther in honor of Robert John Lechmere Guppy, who sent specimens of the species from Trinidad to the Natural History Museum in London.

[10] Field studies reveal that guppies have colonized almost every freshwater body accessible to them in their natural ranges, especially in the streams located near the coastal fringes of mainland South America.

While wild-type females are grey in body colour, males have splashes, spots, or stripes that can be any of a wide variety of colors.

Brood size is extremely variable, yet some consistent differences exist among populations depending on the predation level and other factors.

[5] Females of matching body sizes tend to produce more numerous but smaller-sized offspring in high-predation conditions.

[19] One major factor that affects wild guppies' senescence patterns is the mortality rate caused by predation.

[17][dubious – discuss] In addition to senescence pattern, resource availability and density also matter in regulation of guppy populations.

For example, during the wet season from May to December, guppies in the Northern Range of Trinidad reduce their investment in reproduction regardless of predation level, possibly in response to decreased food resources.

The cost of multiple mating for males is very low because they do not provide material benefit to the females or parental care to the offspring.

Conversely, multiple mating can be disadvantageous for females because it reduces foraging efficiency and increases the chances of predation and parasitic infection.

In guppies, a post-copulatory mechanism of inbreeding avoidance occurs based on competition between sperm of rival males for achieving fertilization.

[29] Orange spots can serve as an indicator of better physical fitness, as orange-spotted males are observed to swim longer in a strong current.

Because of this connection, females are possibly selecting for healthy males with superior foraging abilities by choosing mates with bright orange carotinoid pigments, thus increasing the survival chance of her offspring.

[32] Due to the advantage in mating, male guppies evolve to have more ornamentation across generations in low-predation environments where the cost of being conspicuous is lower.

[35] Guppies' small bodies and the bright coloration of males make them easy prey, and like many fish, they often school together to avoid predation.

Male guppies evolve to be more dull in color and have fewer, smaller spots under intense predation both in wild and in laboratory settings.

[44] Recent work on this has shown that the interaction between exposure to chronic anthropogenic noise and G. turnbulli can decrease guppy survival.

[44] Wild guppies feed on algal remains, diatoms, invertebrates, zooplankton, detritus,[45] plant fragments, mineral particles, aquatic insect larvae, and other sources.

Studies also show when an evolutionary cost exists, guppies that tend to shoal are less aggressive and less competitive with regards to scarce resources.

[50] The gestation period of guppies varies considerably, ranging from 20 to 60 days at 25 to 27 C and depending on several environmental factors.

[57][58] Due to the extensive selective breeding of guppies for desirable traits such as greater size and colour, some strains of the fish have become less hardy than their wild counterparts.

Guppies should not be kept as a single fish in an aquarium because both males and females show signs of shoaling, and are usually found in large groups in the wild.

A continuous supply of live food, such as Daphnia or brine shrimp, keep adult fish full and may spare the fry when they are born.

Feeding fry live foods, such as baby brine shrimp, microworms, infusoria and vinegar eels, is recommended.

The primary causative agents of fin rot are gram-negative bacteria such as Pseudomonas fluorescens and Aeromonas hydrophila.

[71] Poor water quality, overcrowding, and stress are significant contributors to the onset and progression of the disease, as they create an environment conducive for bacterial growth and can compromise the fish's immune system.

Common treatment measures include: improving water quality, antibacterial medications such as kanamycin, erythromycin, or oxytetracycline, and in extreme cases, antibiotic injections.

Notable symptoms include a fine gold or rust-colored dust appearing on the fish's body, clamped fins, scratching against objects, rapid gill movement due to irritation, decreased feeding, lethargy, and, in advanced stages, respiratory distress.

This condition is associated with the swim bladder, a gas-filled organ that aids fish in remaining buoyant at varying water depths.