![Selasphorus rufus1](https://upload.wikimedia.org/wikipedia/commons/9/97/Selasphorus_rufus1.jpg)
In
ethology
Ethology is the scientific study of animal behaviour, usually with a focus on behaviour under natural conditions, and viewing behaviour as an evolutionarily adaptive trait. Behaviourism as a term also describes the scientific and objectiv ...
and
behavioral ecology
Behavioral ecology, also spelled behavioural ecology, is the study of the evolutionary basis for animal behavior due to ecological pressures. Behavioral ecology emerged from ethology after Niko Tinbergen outlined four questions to address when ...
, trap-lining or traplining is a feeding strategy in which an individual visits food sources on a regular, repeatable sequence, much as
trappers
Animal trapping, or simply trapping or gin, is the use of a device to remotely catch an animal. Animals may be trapped for a variety of purposes, including food, the fur trade, hunting, pest control, and wildlife management.
History
Neolithic ...
check their lines of traps.
Traplining is usually seen in species foraging for floral resources.
This involves a specified route in which the individual traverses in the same order repeatedly to check specific plants for flowers that hold nectar, even over long distances. Trap-lining has been described in several
taxa
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
, including
bees
Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfamil ...
,
butterflies
Butterflies are insects in the macrolepidopteran clade Rhopalocera from the Order (biology), order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The ...
,
tamarins
The tamarins are squirrel-sized New World monkeys from the family Callitrichidae in the genus ''Saguinus''. They are the first offshoot in the Callitrichidae tree, and therefore are the sister group of a clade formed by the lion tamarins, Goe ...
,
bats
Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
,
rats
Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' (pack rats), ''Bandicota'' (bandicoot ...
, and
hummingbirds
Hummingbirds are birds native to the Americas and comprise the biological family Trochilidae. With about 361 species and 113 genera, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropics aro ...
and tropical
fruit-eating mammals such as
opossums
Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North A ...
,
capuchins
Capuchin can refer to:
*Order of Friars Minor Capuchin
The Order of Friars Minor Capuchin (; postnominal abbr. O.F.M. Cap.) is a religious order of Franciscan friars within the Catholic Church, one of Three " First Orders" that reformed from t ...
and
kinkajous.
Traplining is used to term the method in which bumblebees and hummingbirds go about collecting nectar, and consequently,
pollinating
Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds, a ...
each plant they visit. The term "traplining" was originally coined by
Daniel Janzen
Daniel Hunt Janzen (born January 18, 1939 in Milwaukee, Wisconsin) is an American evolutionary ecologist, and conservationist. He divides his time between his professorship in biology at the University of Pennsylvania, where he is the DiMaura ...
,
although the concept was discussed by
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...
and
Nikolaas Tinbergen
Nikolaas "Niko" Tinbergen (; ; 15 April 1907 – 21 December 1988) was a Dutch biologist and ornithologist who shared the 1973 Nobel Prize in Physiology or Medicine with Karl von Frisch and Konrad Lorenz for their discoveries concerning the or ...
.
Behavioral response
In the instance of hummingbirds and bumblebees, traplining is an evolutionary response to the allocation of resources between species.
Specifically, individual hummingbirds form their own specific routes in order to minimize competition and maximize nutrient availability. Some hummingbird species are territorial (e.g.
rufous hummingbird, ''Selasphorus rufus'',) and defend a specific territory, while others are trapliners (i.e.
Long-billed hermit
The long-billed hermit (''Phaethornis longirostris'') is a bird in the family Trochilidae, the hummingbirds. It is found from central Mexico south through Central America, Colombia and Ecuador into Peru.
Taxonomy and systematics
It has oft ...
, ''Phaethornis longirostris'') and constantly check different locations for food. Because of this, territorial hummingbirds will be more robust, while traplining hummingbirds have adaptations such as longer wings for more efficient flying.
Traplining hummingbirds will move from source to source, obtaining nectar from each. Over time, one hummingbird will be the primary visitor to a particular source.
In the case of bumblebees, when competitors are removed, there is an influx to the removal area and less time is spent traplining over long distances. This demonstrates the ability to behaviorally adapt based on surrounding competition.
In addition, bumblebees use traplining to distinguish between high nectar-producing flowers and low-nectar producing flowers by consistently recognizing and visiting those that produce higher levels.
Other types of bees, such as with euglossine bees (i.e. ''
Euglossa imperialis'') use traplining to forage efficiently by flying rapidly from one precise flowering plant to the next in a set circuit, even ignoring newly blooming plants which are adjacent, but outside, of its daily route. By doing so, these euglossine bees significantly reduce the amount of time and energy spent searching for nectar each day. In general, it is seen that traplining species have higher nutritional rewards than non-traplining species.
Energy conservation
Traplining hummingbirds are known to be active proportionally to nectar production in flowers, decreasing throughout the day. Therefore, traplining hummingbirds can spend less time foraging, and obtain their energy intake from a few number of flowers.
Spending less time searching for food means less energy spent flying and searching. Traplining bumblebees prioritize their routes based on travel distance and reward quantity.
It is seen that the total distance of the trapline is related to the abundance of the reward (nectar) in the environment.
Spatial cognition and memory
Traplining can also be an indication of the levels of
spatial cognition
Spatial cognition is the acquisition, organization, utilization, and revision of knowledge about spatial environments. It is most about how animals including humans behave within space and the knowledge they built around it, rather than space itse ...
of species that use the technique. For example, traplining in bumblebees is an indication that bumblebees have spatial reference memory, or
spatial memory
In cognitive psychology and neuroscience, spatial memory is a form of memory responsible for the recording and recovery of information needed to plan a course to a location and to recall the location of an object or the occurrence of an event. Sp ...
, that is used to create specific routes in short term foraging.
The ability to remember specific routes long-term cuts down foraging and flying time, consequently conserving energy. This theory has been tested, showing that bumblebees can remember the shortest route to the reward, even when the original path has been changed or obstructed.
Additionally, bees cut down the amount of time spent revisiting sites with little or no nutritive reward.
Bees with access to only
short-term memory
Short-term memory (or "primary" or "active memory") is the capacity for holding a small amount of information in an active, readily available state for a short interval. For example, short-term memory holds a phone number that has just been recit ...
forage inefficiently.
Advantages
One of the main advantages of traplining is that the route can be taught to other members of the population quickly or over a period of hours, leading all members to a reliable food source. When the group works together on finding a particular source of food they can quickly establish where it is and get the route information transferred to all the individuals in the population. This ensures that the entire community is able to quickly find and consume the nutrients that are needed.
Traplining helps foragers that are competing for resources that replenish in a decelerating way. For example, nectar in a plant is slowly replaced over time, while acorns only occur once a year.
Traplining can help plant diversity and evolution by keeping pollen with different genetics flowing from plant to plant. It is mostly pollinators that use traplining as a way to ensure they always know where the food sources they are looking for are. This means that organisms like bumblebees and hummingbirds can transfer pollen anywhere from the starting point of the route to the final food source along the path. Since the path is always the same, it greatly reduces the risk of
self-pollination
Self-pollination is a form of pollination in which pollen from the same plant arrives at the Stigma (botany), stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). There are two types of self-pollination: in autogamy, pollen i ...
(iterogamy) because the pollinator won't return to the same flower on that particular foraging session.
Overall, plant species that are visited by trapliners have increased fitness and evolutionary advantages.
Because of this mutualistic relationship between traplining hummingbirds and plants, traplining hummingbirds have been referred to as "legitimate pollinators", while territorial hummingbirds have been referred to as "nectar thieves".
If an organism that traplines learns where a food source is once, they can always return to that food source because they can remember minute details about the location of the source. This allows them to adapt quickly if one of the major sources suddenly becomes scarce or destroyed.
Disadvantages
Serious obstacles, such as the arrangement of plant life, can hamper traplining. If the route zig zags through the understory of the tropical rainforest, some of the organisms using the route can get lost because of very subtle changes,
such as a
treefall gap
A treefall gap is a distinguishable hole in the canopy of a forest with vertical sides extending through all levels down to an average height of above ground. These holes occur as result of a fallen tree or large limb. The ecologist who develop ...
or heavy rainfall. This could cause an individual to be separated from the entire group if it isn't able to find the path back to the original route. Some food sources can be overlooked because the traplining route in use does not lead the organisms to the area that these resources are in.
Since the route is very specific, the organisms following it may also miss out on opportunities to come in contact with potential mates. Male bumblebees going directly to the source of food have been observed to pass up on female bumblebees as potential mates that are along the same path, preferring to continue foraging and bring food back to the hive.
This can take away from species diversification and could possibly delete some traits in the
gene pool
The gene pool is the set of all genes, or genetic information, in any population, usually of a particular species.
Description
A large gene pool indicates extensive genetic diversity, which is associated with robust populations that can surv ...
that are useful.
Research
Observing traplining in the natural world has proven to be very difficult and little is known about how and why species trapline, but the study of traplining in the natural environment does take place. In one particular study, individual bees trained on five artificial flowers of equal reward were observed traplining between those five flowers. When a new flower of higher reward gets included in the group, the bees subsequently adjust their trapline to include the higher reward flower. Under natural conditions they hypothesized that it would likely be beneficial for bees to prioritize higher reward flowers to either beat out competition or conserve energy.
In other field experiments, ecologists created a "competition vacuum" to observe whether or not bumblebees adjusted their feeding routes based on intense direct competition between other bumblebees. This study showed that bees in areas of higher competition are more productive than the control bees. Bumblebees opportunistically adjust their use of traplining routes in response to activity of other competing bees.
Another effective way to study the behavior of traplining species is via computer simulation and indoor flight cage experiments. Simulation models can be made to show the linkage between pollinator movement and pollen flow. This model considers how service by the pollinators with different foraging patterns would affect the flow of pollen.
Indoor flight cage experiments allow for easier determination between test subjects and easier observation of behavior and patterns. Bees in small study environments seem to demonstrate less traplining tendencies than bees that were studied in environments that stretched over several hectares. A larger working area increases the need for traplining techniques to further conserve energy and maximize nutrient intake and that bees most often trapline due strictly to travel distance. The bees remember these complex flight paths by breaking them into small segments using vectors, landmarks and other environmental factors, each one pointing to the next destination.
Despite a long history of research on bee learning and navigation, most knowledge has been deduced from the behavior of foragers traveling between their nest and a single feeding location.
Only recently, studies of bumblebees foraging in arrays of artificial flowers fitted with automated tracking systems have started to describe the learning mechanisms behind complex route formation between multiple locations. The demonstration that all these observations can be accurately replicated by a single learning heuristic model holds considerable promises to further investigate these questions and fill a major gap in cognitive ecology.
See also
*
Optimal foraging theory
Optimal foraging theory (OFT) is a behavioral ecology model that helps predict how an animal behaves when searching for food. Although obtaining food provides the animal with energy, searching for and capturing the food require both energy and t ...
References
{{reflist
Eating behaviors
Bird behavior