page_title: Dear enemy effect
section_title: Nasty neighbour effect or no effect
hierarchical_section_title: Dear enemy effect / Nasty neighbour effect or no effect
caption_attribution_description: Oophaga pumilio from Cologne Zoo, Germany
context_page_description: The dear enemy effect or dear enemy recognition is an ethological phenomenon in which two neighbouring territorial animals become less aggressive toward one another once territorial borders are well established. As territory owners become accustomed to their neighbours, they expend less time and energy on defensive behaviors directed toward one another. However, aggression toward unfamiliar neighbours remains the same. Some authors have suggested the dear enemy effect is territory residents displaying lower levels of aggression toward familiar neighbours compared to unfamiliar individuals who are non-territorial "floaters".
  The dear enemy effect has been observed in a wide range of animals including mammals, birds, reptiles, amphibians, fish and invertebrates. It can be modulated by factors such as the location of the familiar and unfamiliar animal, the season, and the presence of females.
  The effect is the converse of the nasty neighbour effect, in which some species are more aggressive towards their neighbours than towards unfamiliar strangers.
context_section_description: A range of studies have found evidence of an effect opposite to the dear enemy effect, i.e. more aggression is shown toward neighbours than strangers.  This has been termed the "nasty neighbour" effect.
  Colonies of the weaver ant (Oecophylla smaragdina) are able to recognize a greater proportion of workers from neighbouring colonies as non-colony members.  When recognized as non-colony members, more aggression is exhibited toward neighbours than non-neighbours.  Banded mongoose (Mungos mungo) groups vocalize more and inspect more scent samples in response to olfactory cues of neighbours than strangers.  It has been suggested that increased aggression towards neighbours is more common in social species with intense competition between neighbours, as opposed to reduced aggression towards neighbours typical for most solitary species.  Furthermore, animals may respond in this way when encounters with intruders from non-neighbouring colonies are rare and of little consequence.
  Female New Zealand bellbirds (Anthornis melanura) are more aggressive toward the songs of neighbouring females. This is opposite to the dear enemy phenomenon and suggests that neighbouring females pose a greater threat than strangers in this species.
  A range of studies have found no evidence of the dear enemy effect showing the effect is not universal. Territorial males of the strawberry dart-poison frog (Dendrobates pumilio) and the spotted antbird (Hylophylax naevioides) do not discriminate behaviourally between the calls of neighbours and strangers, and female collared lizards show no difference in their behaviour to neighbouring or unfamiliar females.
  Guinea baboon (Papio papio) males which live in gangs do not differ in their response behaviour toward neighbouring and stranger males and largely ignore any non-gang member, irrespective of familiarity; that is, they neither show a “dear enemy” nor “nasty neighbour” effect.
caption: Strawberry dart-poison frog
exif: {"Image ImageDescription": "OLYMPUS DIGITAL CAMERA", "Image Make": "OLYMPUS IMAGING CORP.", "Image Model": "E-330", "Image Orientation": "Horizontal (normal)", "Image XResolution": "314", "Image YResolution": "314", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Version 1.2", "Image DateTime": "2007:09:08 16:03:30", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "828", "Image PrintIM": "[80, 114, 105, 110, 116, 73, 77, 0, 48, 51, 48, 48, 0, 0, 37, 0, 1, 0, 20, 0, ... ]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "3974", "Thumbnail JPEGInterchangeFormatLength": "5597", "EXIF ExposureTime": "1/180", "EXIF FNumber": "11", "EXIF ExposureProgram": "Aperture Priority", "EXIF ISOSpeedRatings": "200", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2007:09:08 16:03:30", "EXIF DateTimeDigitized": "2007:09:08 16:03:30", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "761/256", "EXIF MeteringMode": "Spot", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash fired, compulsory flash mode", "EXIF FocalLength": "150", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3136", "EXIF ExifImageLength": "2352", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "3850", "EXIF FileSource": "Digital Camera", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "Low gain up", "EXIF Contrast": "Normal", "EXIF Saturation": "Hard", "EXIF Sharpness": "Normal"}