Dynamic changes in alarm call structure: a strategy for reducing conspicuousness to avian predators?

Behaviour ◽  
2003 ◽  
Vol 140 (3) ◽  
pp. 353-369 ◽  
Author(s):  
Christopher Evans ◽  
Karen Bayly
Keyword(s):  
Broad Band ◽  
Alarm Call ◽  
High Amplitude ◽  
Dominant Frequency ◽  
Adaptive Plasticity ◽  
Alarm Calls ◽  
Potential Predator ◽  
Call Structure ◽  
Avian Predators ◽  
Signal Efficacy

AbstractThe design of many animal signals reflects the need to maximize signal efficacy while minimizing conspicuousness to eavesdroppers. The aerial alarm calls of birds have been a useful model system for exploring such evolutionary tradeoffs at the level of general call structure, but much less is known about changes in fine-scale signal characteristics over the course of an encounter with a potential predator. We analyzed variation in the alarm calls that male fowl, Gallus gallus, produced in response to raptor silhouettes moving overhead. Spectrogram cross-correlation was used to test for changes in structure over the course of a call bout. This analysis revealed that aerial alarm calls are individually distinctive and that they vary significantly from the first call to the second. We then measured single acoustic parameters, including the duration, dominant frequency and frequency bandwidth of each component in successive calls. Males almost invariably began the first call in a bout with a high amplitude broad-band pulse, which was followed by a much longer and highly variable sustained element. They then selectively reduced or eliminated the introductory pulse, while leaving other aspects of alarm structure unchanged. Recent work has shown that the introductory pulse is potentially costly because it has attributes that are readily localized by raptors. We suggest that male fowl have adaptive plasticity in alarm call structure, allowing them to manage short-term predation risk while continuing to signal to companions.

Semantics of an Avian Alarm Call System: the Male Domestic Fowl, Gallus Domesticus

Behaviour ◽  
1987 ◽  
Vol 102 (1-2) ◽  
pp. 15-39 ◽  
Author(s):  
Peter Marler ◽  
Roberta Pickert ◽  
Marcel Gyger
Keyword(s):  
Good Predictor ◽  
Domestic Fowl ◽  
Stimulus Object ◽  
Angular Size ◽  
Alarm Call ◽  
Alarm Calls ◽  
General Function ◽  
Contingency Table Analysis ◽  
Predator Detection ◽  
Call Structure

AbstractVocal alarm signals of male domestic fowl given in the presence of predators and other ground and aerial objects were recorded and analyzed. Studies were conducted under semi-naturalistic conditions and a telemetric technique was used to facilitate high quality sound recording. Cockerels gave ground alarm calls specifically to objects moving on the substrate and aerial alarm calls to objects moving above in free space. Vocalizations were associated with both dangerous and harmless objects. We therefore investigated variation in sound structure of aerial alarm calls with reference to flying predators and non-predators. A multidimensional contingency table analysis revealed a significant tendency for qualitatively different aerial alarm calls to be associated with flying predators and non-predators. Differences in call structure were restricted to the two first units of the alarm call. We tested the hypotheses that variation in aerial alarm call structure might be affected by either the distance separating the bird from the object or the angular size of the object projected onto the retina of the cockerel. Statistical analysis showed that the angular size was a good predictor of variation of the second unit of alarm call. The distance it self was less predictive. The first unit of the alarm call was not affected by either the distance or the angular size of the object. We propose that this part of the call has a more general function of alerting the conspecific companions. We conclude that alarm vocalizations of male domestic fowl refer specifically to a certain type of stimulus object, either moving on the ground or flying. For alarm calls correlated with aerial stimuli the specific angular size of a stimulus object moving in the air is a good predictor of call structure. We suggest that this way of dealing with flying objects as stimuli for alarm calls is the result of a predator detection strategy in which the benefits of an expanded field of vision, an important adaptation for ground-dwelling birds, exceed the costs of alarming to harmless birds and other aerial objects.

scholarly journals Discrimination of Acoustic Stimuli and Maintenance of Graded Alarm Call Structure in Captive Meerkats

Animals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3064
Author(s):  
Sebastian Schneider ◽  
Sarah Goettlich ◽  
Charlette Diercks ◽  
Paul Wilhelm Dierkes
Keyword(s):  
Clustering Algorithm ◽  
Escape Behavior ◽  
Cooperative Behavior ◽  
Alarm Call ◽  
Acoustic Signals ◽  
Alarm Calls ◽  
Call Structure ◽  
Graded Structure ◽  
Suricata Suricatta ◽  
In Captivity

Animals living in human care for several generations face the risk of losing natural behaviors, which can lead to reduced animal welfare. The goal of this study is to demonstrate that meerkats (Suricata suricatta) living in zoos can assess potential danger and respond naturally based on acoustic signals only. This includes that the graded information of urgency in alarm calls as well as a response to those alarm calls is retained in captivity. To test the response to acoustic signals with different threat potential, meerkats were played calls of various animals differing in size and threat (e.g., robin, raven, buzzard, jackal) while their behavior was observed. The emitted alarm calls were recorded and examined for their graded structure on the one hand and played back to them on the other hand by means of a playback experiment to see whether the animals react to their own alarm calls even in the absence of danger. A fuzzy clustering algorithm was used to analyze and classify the alarm calls. Subsequently, the features that best described the graded structure were isolated using the LASSO algorithm and compared to features already known from wild meerkats. The results show that the graded structure is maintained in captivity and can be described by features such as noise and duration. The animals respond to new threats and can distinguish animal calls that are dangerous to them from those that are not, indicating the preservation of natural cooperative behavior. In addition, the playback experiments show that the meerkats respond to their own alarm calls with vigilance and escape behavior. The findings can be used to draw conclusions about the intensity of alertness in captive meerkats and to adapt husbandry conditions to appropriate welfare.

ALARM CALLING IN THREE SPECIES OF MARMOTS

Behaviour ◽  
1999 ◽  
Vol 136 (6) ◽  
pp. 731-757 ◽  
Author(s):  
Daniel Blumstein
Keyword(s):  
Alarm Call ◽  
Vancouver Island ◽  
Alarm Calls ◽  
Playback Experiments ◽  
Micro Structure ◽  
Stimulus Class ◽  
Call Structure ◽  
Alarm Calling ◽  
Degree Of Risk ◽  
Lines Of Evidence

AbstractMany species produce alarm calls that vary according to situation. Theoretically, alarm call structure could covary with predator type and could communicate potentially ''referential information, or calls could covary with the degree of risk a caller experienced when it emitted a call. Using similar methods, I studied the ways in which Olympic (Marmota olympus), hoary (M. caligata), and Vancouver Island marmots (M. vancouverensis) communicated situational variation. I observed both natural alarm calling, and I artificially elicited alarm calls with simulated terrestrial and aerial predators. I used playback experiments to study marmots' responses to different alarm call variants. All three species produced four roughly similar but distinctive loud alarm vocalizations that could be categorized by their relative shape, duration, and whether calls were quickly repeated to create multi-note vocalizations. In addition, the Vancouver Island marmot produced a fifth loud alarm call-the kee-aw. Call micro-structure varied as a function of the distance the caller was from an alarming stimulus and the type of alarming stimulus. Two lines of evidence suggest that all three species had alarm calls associated with the caller's risk (i.e. they were not referential). First, marmots often changed call types within a calling bout: there were no unique stimulus-class specific vocalizations. Second, marmot responses to alarm calls were graded: marmots did not have unique responses to different call types. These three close taxonomic relatives with superficially similar calls, communicated risk differently.

Perception of terrestrial and aerial alarm calls by honeyeaters and falcons

2000 ◽  
Vol 48 (2) ◽  
pp. 127 ◽  
Author(s):  
Sharon R. Wood ◽  
Ken J. Sanderson ◽  
Christopher S. Evans
Keyword(s):  
Computer System ◽  
Prey Species ◽  
Narrow Band ◽  
Broad Band ◽  
Alarm Calls ◽  
Avian Predators ◽  
Noisy Miner ◽  
Distress Calls ◽  
Manorina Melanocephala ◽  
Reduce Risk

This study tested the responses to aerial and terrestrial alarm and distress calls in an avian predator, the brown falcon, Falco berigora, and two potential avian prey species, the New Holland honeyeater, Philidonyris novaehollandiae, and noisy miner, Manorina melanocephala. Calls were delivered from a computer system at intensities 5–20 dB above background, to birds held in large cages. All birds located the broad-band alarm and distress calls easily, but they had difficulty locating the narrow-band aerial alarm calls, although they were able to detect most of these. Aerial alarm calls thus reduce risk to the caller. The performance of raptors and songbirds was similar. This result suggests that there are no reliable differences in the auditory characteristics of avian predators and prey, as have been described in species from the Northern Hemisphere.

Context-specific alarm calls of the eastern chipmunk, Tamias striatus

1994 ◽  
Vol 72 (6) ◽  
pp. 1087-1092 ◽  
Author(s):  
Karen Burke da Silva ◽  
Donald L. Kramer ◽  
Daniel M. Weary
Keyword(s):  
High Frequency ◽  
Alarm Call ◽  
Alarm Calls ◽  
Field Site ◽  
Tamias Striatus ◽  
Avian Predators ◽  
Repeated Calls ◽  
Lower Amplitude ◽  
Mammalian Predators ◽  
Context Specific

The structure and context of alarm calls produced by chipmunks (Tamias striatus) at a field site in southern Quebec were recorded during opportunistic field observations and experimentally simulated hawk attacks. Chipmunks produced three call types in the presence of predators. Chipping consisted of a series of high frequency notes with a rapid downward frequency slope (9.6 to 2.8 kHz) and was given in the presence of mammalian predators by chipmunks perched on a raised vantage point. Chucking consisted of a series of lower frequency notes also sloping downwards (2.5 to 0.4 kHz), given in the presence of avian predators by perched animals. The trill was a lower amplitude, multi-note call usually given only once by animals before reaching a refuge while fleeing from either type of predator. The average trill contained 6–11 downward sloping notes (7.3 to 0.8 kHz). The alarm call types of eastern chipmunks appear to be similar to those reported for western chipmunks. However, they differ in the clear separation of the calls for aerial and terrestrial predators. Chipmunks differ from most other terrestrial sciurids in giving repeated calls for aerial as well as terrestrial predators and in using a call just before reaching a secure refuge.

The Analysis and Simulation of Contact Loss between Pantograph and Catenary on Electric Railway

2015 ◽  
Vol 713-715 ◽  
pp. 1277-1280
Author(s):  
Yin Han Gao ◽  
Ju Xian Wang ◽  
Kai Yu Yang ◽  
Tian Hao Wang ◽  
Zhan Yang An
Keyword(s):  
Equivalent Circuit ◽  
Electromagnetic Interference ◽  
Broad Band ◽  
High Amplitude ◽  
Matlab Simulink ◽  
Arc Model ◽  
Traction Network ◽  
Electric Railway ◽  
The Moment

Based on the classical Mayer-arc model, this paper establishes the equivalent circuit of traction network for AC25kV electric railway from the essence of contact loss discharge. The voltage waves of contact loss arc at different moments are obtained by MATLAB/simulink. Through the analysis, it can be confirmed that the EMI (electromagnetic interference) with broad band and high amplitude will appear at the moment the contact loss between pantograph and catenary happens. Finally, relevant measures are given to avoid the probability event of contact loss.

Progressive Adaptation of the Soleus H-Reflex With Daily Training at Walking Backward

2003 ◽  
Vol 89 (2) ◽  
pp. 648-656 ◽  
Author(s):  
Cyril Schneider ◽  
Charles Capaday
Keyword(s):  
Motor Program ◽  
High Amplitude ◽  
H Reflex ◽  
Adaptive Plasticity ◽  
Reflex Activity ◽  
Reflex Modulation ◽  
Surprising Result ◽  
Backward Walking ◽  
Rehabilitation Programs ◽  
Daily Training

When untrained subjects walk backward on a treadmill the amplitude of the soleus H-reflex in midswing is equal to or exceeds the value in stance. This is a surprising result because during the swing phase of backward walking the soleus is inactive and its antagonist, the tibialis anterior, is active. We suggested that the high amplitude of the soleus H-reflex in late swing reflects task uncertainties, such as estimating the moment of foot contact with the ground and losing balance. In support of this idea we show that when untrained subjects held on to handrails the unexpected high-amplitude H-reflex during midswing was no longer present. We therefore asked whether daily training at this task without grasping the handrails would adaptively modify the H-reflex modulation pattern. In this event, within 10 days of training for 15 min daily, the anticipatory reflex activity at the beginning of training was gradually abated as the subjects reported gaining confidence at the task. However, when adapted subjects were made to walk backward with their eyes shut, the anticipatory reflex activity in midswing returned immediately. The reflex changes as a result of training were not due to changes in the motor activity or kinematics; they are likely part of the motor program controlling backward walking. This adaptive phenomenon may prove to be a useful model for studying the neural mechanisms of motor learning and adaptive plasticity in humans and may be relevant to rehabilitation programs for neurological patients.

scholarly journals Heterospecific alarm-call recognition in two warbler hosts of common cuckoos

2019 ◽  
Vol 22 (6) ◽  
pp. 1149-1157 ◽  
Author(s):  
Jiangping Yu ◽  
Hailin Lu ◽  
Wei Sun ◽  
Wei Liang ◽  
Haitao Wang ◽  
...  
Keyword(s):  
Alarm Call ◽  
Alarm Calls ◽  
Reed Warbler ◽  
Cuculus Canorus ◽  
Common Cuckoo ◽  
Playback Experiments ◽  
Call Recognition ◽  
Accipiter Nisus ◽  
Main Host ◽  
The Common

Abstract Species facing similar selection pressures should recognize heterospecific alarm signals. However, no study has so far examined heterospecific alarm-call recognition in response to parasitism by cuckoos. In this study, we tested whether two sympatric host species of the common cuckoo Cuculus canorus, Oriental reed warbler Acrocephalus orientalis (ORW, main host), and black-browed reed warbler Acrocephalus bistrigiceps (BRW, rare host), could recognize each other’s alarm calls in response to cuckoos. Dummies of common cuckoo (parasite) and Eurasian sparrowhawk Accipiter nisus (predator) were used to induce and record alarm calls of the two warbler species, respectively. In the conspecific alarm-call playback experiments, ORW responded more strongly to cuckoo alarm calls than to sparrowhawk alarm calls, while BRW responded less strongly to cuckoo alarm calls than to sparrowhawk alarm calls. In the heterospecific alarm-call playback experiments, both ORW and BRW responded less strongly to cuckoo alarm calls than sparrowhawk alarm calls. BRW seemed to learn the association between parasite-related alarm calls of the ORW and the cuckoo by observing the process of ORW attacking cuckoos. In contrast, alarm calls of BRW to cuckoos were rarely recorded in most cases. BRW with low parasite pressure still developed recognition of heterospecific parasite-related alarm call. Unintended receivers in the same community should recognize heterospecific alarm calls precisely to extract valuable information.

scholarly journals Specific responses of cuckoo hosts to different alarm signals according to breeding stage: a test of the offspring value hypothesis

2020 ◽  
Vol 66 (6) ◽  
pp. 649-655 ◽  
Author(s):  
Jiaojiao Wang ◽  
Canchao Yang
Keyword(s):  
Alarm Call ◽  
Host Responses ◽  
Alarm Calls ◽  
Attack Behavior ◽  
Brood Parasite ◽  
Reed Warbler ◽  
Defense Strategies ◽  
Breeding Stage ◽  
Accipiter Nisus ◽  
Streptopelia Orientalis

Abstract The selective pressure exerted by avian brood parasites forces their hosts to evolve specific defense strategies. When subject to brood parasite attack, avian hosts will often emit alarm calls. To date, few studies have examined whether and how host responses to different alarm calls indicative of different enemies vary with the host’s breeding stage. We carried out alarm call playback experiments during both the egg and nestling stages of the oriental reed warbler Acrocephalus orientalis, a host of the common cuckoo Cuculus canorus. The playback exemplars were selected from recorded alarm calls of the warbler to the presence of common cuckoos, sparrowhawks Accipiter nisus, and oriental turtle doves Streptopelia orientalis, which represented brood parasite, predator, and harmless control, respectively. The results showed that the oriental reed warblers did not discriminate alarm calls issued to different intruder types, but the intensity of the response was significantly higher in the nestling stage than in the egg stage. Attack behavior related to sparrowhawk alarm calls was absent in the egg stage, but aggressive behavior increased dramatically and exceeded the attack frequency in response to the cuckoo alarm call in the nestling stage, implying a shift in the tradeoff between the parents’ own survival and the loss of offspring. Alarm calls attracted a larger number of conspecifics than members of other species. In general, the oriental reed warbler had consistently stronger responses to different alarm calls in the nestling stage than in the egg stage, supporting the offspring value hypothesis.

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