title: Foraging ants trade off further for faster: use of natural bridges and trunk trail permanency in carpenter ants.
abstract: Trail-making ants lay pheromones on the substrate to define paths between foraging areas and the nest. Combined with the chemistry of these pheromone trails and the physics of evaporation, trail-laying and trail-following behaviours provide ant colonies with the quickest routes to food. In relatively uniform environments, such as that provided in many laboratory studies of trail-making ants, the quickest route is also often the shortest route. Here, we show that carpenter ants (Camponotus rufipes), in natural conditions, are able to make use of apparent obstacles in their environment to assist in finding the fastest routes to food. These ants make extensive use of fallen branches, twigs and lianas as bridges to build their trails. These bridges make trails significantly longer than their straight line equivalents across the forest floor, but we estimate that ants spend less than half the time to reach the same point, due to increased carriage speed across the bridges. We also found that these trails, mainly composed of bridges, are maintained for months, so they can be characterized as trunk trails. We suggest that pheromone-based foraging trail networks in field conditions are likely to be structured by a range of potentially complex factors but that even then, speed remains the most important consideration.
authors.forename: Raquel G
authors.initials: RG
authors.lastname: Loreto
authors.forename: Adam G
authors.initials: AG
authors.lastname: Hart
authors.forename: Thairine M
authors.initials: TM
authors.lastname: Pereira
authors.forename: Mayara L  R
authors.initials: ML
authors.lastname: Freitas
authors.forename: David P
authors.initials: DP
authors.lastname: Hughes
authors.forename: Simon L
authors.initials: SL
authors.lastname: Elliot
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology*; D004777:Environment; D005247:Feeding Behavior / Q000502:physiology*; D013997:Time Factors
references.citation: J Theor Biol. 2006 Apr 21;239(4):507-15
references.pmid: 16199059
references.citation: Nature. 2004 Mar 4;428(6978):70-3
references.pmid: 14999281
references.citation: J Insect Physiol. 2008 Mar;54(3):534-42
references.pmid: 18221944
references.citation: Oecologia. 1998 Dec;117(3):404-412
references.pmid: 28307920
references.citation: PLoS One. 2012;7(5):e36352
references.pmid: 22567151
references.citation: Am Nat. 2009 Sep;174(3):424-33
references.pmid: 19627240
references.citation: Ecology. 2010 Jan;91(1):65-72
references.pmid: 20380197
references.citation: J Exp Biol. 2011 Aug 15;214(Pt 16):2730-8
references.pmid: 21795570
references.citation: Nature. 2004 Dec 16;432(7019):907-9
references.pmid: 15602563
references.citation: Oecologia. 2000 Aug;124(2):156-165
references.pmid: 28308174
references.citation: J Exp Biol. 2011 Jan 1;214(Pt 1):50-8
references.pmid: 21147968