ANIMAL BEHAVIOUR, 2008, 75, 1921e1925 doi:10.1016/j.anbehav.2007.10.037

Available online at www.sciencedirect.com

Cultural learning of predator recognition in mixed-species assemblages of frogs: the effect of tutor-to-observer ratio MAUD C. O. FERRAR I & D OUGLAS P. CHI VERS

Department of Biology, University of Saskatchewan (Received 4 July 2007; initial acceptance 5 September 2007; final acceptance 26 October 2007; published online 15 April 2008; MS. number: A10807)

Animals that live in social groups have the opportunity to acquire information about foraging opportunities, mates and predators. Traditionally, social learning has been studied in birds and mammals, but few tests have been conducted on less social taxa such as amphibians. Moreover, few studies have considered cross-species learning among members of mixed-species assemblages. We examined social learning in tadpoles of the boreal chorus frog, Pseudacris maculata, and found that they do not display a fright response to the odour of predacious tiger salamanders, Ambystoma tigrinum, without prior experience with salamanders, but they can learn to recognize the salamanders when they are paired with predatorexperienced woodfrog, Rana sylvatica, tadpoles. Moreover, the efficacy of learning is enhanced when the ratio of tutors-to-observers increases. Social learning has far-reaching implications for survival of individuals in mixed-species assemblages. Ó 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Keywords: boreal chorus frog; larval amphibians; learned predator recognition; mixed-species assemblages; Pseudacris maculata; Rana sylvatica; social learning; tutor-to-observer ratio; woodfrog

Many animals living in groups have the ability to learn novel information or behaviours by observing nearby conspecifics. For instance, na€ıve birds can learn to locate rewarding foraging areas by watching experienced conspecifics (Ward & Zahavi 1973; reviewed by Galef & Giraldeau 2001). Social learning has also been shown in the context of reproduction. For example, young female guppies, Poecilia reticulata, choose mates according to the choice of older, more experienced conspecific females (Dugatkin & Godin 1992). Social learning of predator recognition has been shown in a variety of taxa. Much of the early work in this field concentrated on birds (Curio et al. 1978; Vieth et al. 1980; Curio 1988). For example, zebra finches, Taeniopygia guttata, and European blackbirds, Turdus merula, learn to mob a novel bird by observing the mobbing response of conspecifics. The conditioned response towards the novel bird is transmitted along a chain of at least six individuals (Curio et al. 1978). Likewise, Herzog & Hopf (1984) showed that juvenile squirrel monkeys, Saimiri sciureus, learn to avoid stuffed Correspondence: M. C. O. Ferrari, Department of Biology, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada (email: maud.ferrari@ usask.ca). 0003e 3472/08/$34.00/0

toy animals (snakes or tigers) when alarm calls are given in association with the stuffed toy. Griffin & Evans (2003) also found that na€ıve tammar wallabies, Macropus eugenii, could learn to recognize a model fox as a threat by observing a conspecific displaying a fearful response to the model fox. The same phenomenon has been shown in fishes (Mathis et al. 1996; Ferrari et al. 2005). Social learning in a variety of contexts appears to be widespread among mammals, birds and fishes (Griffin 2004). However, the degree to which social learning influences behaviour in other taxa appears somewhat limited (Griffin 2004); however, this limitation may be due to a lack of research on those taxa. For example, only one study has considered social learning of predator recognition by larval amphibians (Ferrari et al. 2007a). Tadpoles are known to aggregate. Aggregations, however, have been more generally considered in the context of foraging, where moving aggregations stir up the bottom, thereby suspending particles of food (Duellman & Trueb 1994). Despite the apparent lack of complex social organization, Ferrari et al. (2007a) showed that larval woodfrogs, Rana sylvatica, could learn to recognize the odour of a novel predatory salamander (tiger salamander, Ambystoma tigrinum) when paired with an experienced conspecific. This

1921 Ó 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

1922

ANIMAL BEHAVIOUR, 75, 6

work raised the question of the importance of social learning in amphibians and other taxa that are traditionally considered less social than most birds and mammals. Several studies have examined factors affecting the transmission of social information regarding predation risk. For example, Vilhunen et al. (2005) tested the effect of tutor-to-observer ratio on the transmission of recognition of pikeperch, Sander lucioperca, by Arctic charr, Salvelinus alpinus. With a greater ratio of tutors to observers, one could predict an increase in the transmission of information due to the increase in opportunities for the observers to learn. Contrary to predictions, Vilhunen et al. found that an increase in the number of tutors reduced the ability of na€ıve charr to learn the novel predator. They argued that groups with a large number of knowledgeable individuals reduced the intensity of response of the tutors, due to the dilution effect. The results of Ferrari et al. (2005) suggest that the intensity of the learned response of the observer matches the intensity of the response initially displayed by the tutor. When individual na€ıve fathead minnows, Pimephales promelas, were exposed to a novel cue paired with the sight of three conspecifics displaying various intensities of antipredator behaviour, Ferrari et al. (2005) found a positive correlation between the response intensity of the tutors and the subsequent response intensity of the observer responding to the learned cue. Behavioural ecologists typically consider social learning as transmitting information from knowledgeable tutors to na€ıve conspecifics. However, animals may also learn by observing the behaviour of other species. Only two studies have considered this in the context of social learning of predator recognition. Vieth et al. (1980) showed that European blackbirds could learn to recognize a stimulus as dangerous when exposure to the stimulus was paired with a taped heterospecific chorus of mobbing calls from chaffinches, Fringilla coelebs, great tits, Parus major, and nuthatches, Sitta europaea. Mathis et al. (1996) documented that brook stickleback, Culaea inconstans, could learn to recognize the odour of an unknown predatory pike, Esox lucius, by observing the response of pike-experienced fathead minnows. Cross-species cultural learning deserves more attention, both in the context of learned recognition of risk and learned recognition of food. The purpose of our experiment was two-fold: (1) to test whether cross-species cultural transmission of predator recognition occurs in larval amphibians (i.e. whether chorus frog, Pseudacris maculata, tadpoles could learn to recognize novel tiger salamanders from woodfrog tadpoles) and (2) to test whether the tutor-to-observer ratio affects learning efficacy. We conducted the experiment in three phases: (1) we obtained salamander-na€ıve and salamander-experienced woodfrog tutors, (2) we paired experienced and na€ıve tutors with na€ıve chorus frog observers and exposed them to salamander odour and (3) we subsequently tested the chorus frog observers for a response to salamander odour or a water control. To test for the effect of tutor-to-observer ratio, we paired either two woodfrog tutors with five chorus frog observers, or alternatively five woodfrog tutors with two chorus frog observers. The ability of prey to learn to recognize novel predators has farreaching implications for individual survival.

METHODS

Water, Predators and Test Subjects Five weeks before the experiment, we filled a 1900-litre tub with well water and left it outdoors. The tub was enriched with aquatic plants (sedges: Carex spp, slough grass, horsetail: Equisetum spp.), zooplankton and phytoplankton from a local pond using a fine-mesh dip net. Our use of a fine-mesh dip net ensured that the water (hereafter well water) contained a full array of algae and plankton but no salamander cues. We caught two tiger salamanders (snoutevent length: 18 cm) from a pond on the University of Saskatchewan campus, Saskatoon, in April 2007, using Gee’s Improved minnow traps (cylindrical wire cages, 43 cm long, 22 cm diameter with inverted cone entrances at each end; Tackle Factory, Fillmore, NY, U.S.A.). We kept the salamanders in a 30-litre plastic tub filled with 15 litres of well water and fed them earthworms. We collected four woodfrog egg clutches and 20 boreal chorus frog egg clutches, all of which were laid within a 24 h period, on 27 April 2007 from the same pond in central Alberta. Our field research for the past 4 years has shown that no salamanders were present in this pond, even though they are present in this region of Alberta. Moreover, Ferrari et al. (2007a) found that woodfrog tadpoles from this population do not display fright responses to salamander cues without prior experience with them. No studies have considered whether chorus frogs similarly show no antipredator responses to salamander predators in the absence of experience. We held the tadpoles of the two species separately in two pools (60 cm diameter) containing pond water and aquatic plants until 2 weeks posthatching. The pools were positioned on the pond to equalize the temperature of the pool water with the pond water. After hatching, each tadpole received about two pellets of rabbit food (Essex Top Crop Sales Ltd, ON, Canada) per day to supplement the algae already present in the pools.

Experimental Protocol Training of woodfrog tutors Following the methodology of Ferrari et al. (2007a), we placed two groups of approximately 400 woodfrog tadpoles into two tubs (56  42 cm) containing 47 litres of well water and rabbit chow. We added a tiger salamander to one of the tubs and left the two tubs undisturbed for 3 days. We did not quantify the predation rate on tadpoles in the tub. However, we observed the salamander feeding on tadpoles numerous times and the tadpoles avoiding the area of the tub containing the salamander. After 72 h, we removed the salamander and replaced the water in both tubs with fresh well water. Tadpoles from the tub containing the salamander were considered salamander-experienced tutors and tadpoles from the tub without the salamander were considered salamander-na€ıve tutors.

FERRARI & CHIVERS: SOCIAL LEARNING IN FROG ASSEMBLAGES

Conditioning of chorus frog observers We placed groups of either two or five salamander-na€ıve chorus frog observers in 3.7-litre plastic pails containing 3 litres of well water and added either experienced or na€ıve woodfrog tutors to obtain a total of seven tadpoles per pail. Owing to the size difference between the tadpoles of the two species, we could always identify the woodfrog tadpoles from the chorus frog tadpoles (mean  SD total length of woodfrog tutors: 1.60  0.07 cm; total length of chorus frogs: 1.37  0.01 cm). We let the tadpoles acclimate for 5 h. We then injected 20 ml of salamander odour in each pail and performed a 100% water change 2 h after the injection of the stimulus in the pails. The salamander odour was obtained by placing a salamander in a plastic tub (56  42 cm) containing 15 litres of well water for 3 days. The soaking tub water was used as salamander odour. The salamander used for odour collection was maintained on an earthworm diet and was never fed tadpoles. This ensured that the response of the tadpoles to salamander odour was not confounded by cues emanating from the predator’s diet (reviewed by Chivers & Mirza 2001a).

Testing of chorus frog observers The following day, we placed two chorus frog tadpoles from each bucket in individual 0.5-litre plastic cups filled with well water and left them to acclimate for 1 h. We then exposed one of the two chorus frog observers to 5 ml of salamander odour while exposing the other tadpole to 5 ml of well water. We recorded their behavioural responses using the methodology described below.

Behavioural Assay Numerous studies have established that frog tadpoles decrease activity when exposed to predation risk (e.g. Hokit & Blaustein 1995; Kiesecker & Blaustein 1997; Chivers & Mirza 2001b). To quantify activity, a diameter line was drawn on the bottom of our testing cups and the number of line crosses was counted. A line cross occurred when the entire body of the tadpole crossed over the line. Our testing protocol consisted of quantifying line crosses for 4 min before and 4 min after the injection of the stimulus (5 ml of either salamander odour or well water) in the cup. The stimulus was injected gently on the side of the cup to minimize disturbance. We recorded the antipredator behaviour of 126 tadpoles in a 2  2  2 design testing the effect of tutor experience (na€ıve versus experienced), tutor-to-observer ratio (2 to 5 versus 5 to 2) and cue (water versus salamander odour). At the end of testing all animals were released at their original capture sites.

Statistical Analysis We analysed the change in number of line crosses from the prestimulus baseline using parametric tests, as the data was normally distributed and homoscedastic. The effects of tutor experience, tutor number and cue were analysed

using a mixed-model ANOVA (which included ‘pail’ as a random factor), followed by post hoc tests. The alpha was set to 0.012 using a Bonferroni correction factor for type I errors.

RESULTS The results of the ANOVA are presented in Table 1. The three-way interaction prevented us from concluding on the main effects of the factors, but subsequent post hoc comparisons revealed that, contrary to the responses to water, the responses of chorus frog tadpoles to salamander odour were determined by the experience of the tutors and also the number of tutors involved. Chorus frog tadpoles that were paired with experienced tutors responded to salamander odour with a stronger intensity than did tadpoles that were paired with na€ıve tutors (two na€ıve versus two experienced: P < 0.001; five na€ıve versus five experienced: P < 0.001). Although the number of tutors did not affect the intensity of the tadpoles’ response to salamander odour when tutors were na€ıve (P ¼ 0.994), it did affect the intensity of responses of tadpoles that were paired with experienced tutors. Indeed, tadpoles that were paired with five experienced tutors showed a greater response intensity to salamander odour than did tadpoles that were paired with only two experienced tutors (P ¼ 0.003; Fig. 1).

DISCUSSION Our results provide clear evidence that salamander-na€ıve chorus frog tadpoles do not show antipredator behaviour to salamander odour without prior experience, but they can learn to recognize the cues as a threat when paired with salamander-experienced woodfrog tadpoles. These results raise the possibility that cultural learning in amphibians is indeed widespread. This is only the second species of amphibians for which cultural learning of predator recognition has been considered (see also Ferrari et al. 2007a). Further work should test for social learning of predators in this and other taxa that have traditionally been considered much less social. Even more interesting, researchers should examine cross-species cultural learning. Our experiment clearly shows that chorus frogs that naturally co-occur in the same pond and that share similar

Table 1. Results of the three-way ANOVA testing for the effect of tutor number (2 versus 5), tutor experience (na€ıve versus experienced) and cue (water versus salamander odour) on the learned response of chorus frog tadpoles through social learning Source Number Experience Cue Numberexperience Numbercue Experiencecue Numberexp.cue

df 1, 1, 1, 1, 1, 1, 1,

60.3 60.3 59.6 60.3 59.6 59.6 59.6

F

P

2.6 41.1 39.7 0.7 1.9 46.5 5.0

0.111 <0.001 <0.001 0.415 0.172 <0.001 0.028

1923

ANIMAL BEHAVIOUR, 75, 6

Mean +/– SE change in activity

1924

5 0 –5 –10 –15

2 Naïve

2 Experienced

5 Naïve

5 Experienced

Figure 1. Mean  SE change in activity from the prestimulus baseline of boreal chorus frog tadpoles responding to well water (,) or salamander odour (-). The chorus frog tadpoles were previously paired with two or five woodfrog tutors that were either salamander-na€ıve or salamander-experienced.

predators with woodfrogs can learn to recognize predators through social learning from each other. This is the first documentation of this phenomenon in amphibians. Many groups of animals show mixed-species aggregations (e.g. mammals, birds, amphibians, fishes). Information transfer regarding predation risk may be a prime factor leading to the evolution of multispecies assemblages. In our experiment, we documented that chorus frog tadpoles’ response intensity was higher when tadpoles were paired with five experienced tutors than when they were paired with only two experienced tutors, suggesting that na€ıve observers’ opportunities to learn increased with the number of experienced tutors, resulting in better information transmission. Alternatively, individual tadpoles might use an averaging process to adjust the intensity of their response to a given threat. For example, in our study, each observer was faced either with one nonresponding conspecific and five responding heterospecifics, or with four nonresponding conspecifics and two responding heterospecifics. Whether responses of conspecific chorus frogs and heterospecific woodfrogs are equally reliable from the perspective of a na€ıve chorus frog is unknown, but such reliability could be adaptive because these species share the same predators (salamanders, diving beetles, larval dragonflies, etc.). An unexplored aspect of social learning in amphibians is the exact mode of transmission of the information. In fishes, for example, it has been established that the transmission of the information could be purely visual because observers can learn from watching tutors in an adjacent tank (Ferrari et al. 2005). Likewise, cultural learning of predator recognition by birds is based on the sight of conspecifics mobbing an unknown predator. In larval amphibians, however, visual or mechanical transmissions are both probable mechanisms for learning. If the transmission is based on mechanical stimuli, then we would predict that the higher the number of tutors, the better the rate of transmission. It is important to realize that tadpoles’ antipredator response is to reduce activity. Consequently, the decrease in mechanical disturbance that is associated with the antipredator response of the tutors will be linked to the ratio of active versus nonactive tadpoles. Moreover, in our case, woodfrog tadpoles were

larger than the chorus frog tadpoles, and it is likely that larger individuals create more disturbances, and thus induced a higher decrease in disturbance following the injection of the cues. Social learning is categorized into several types of cognitive mechanisms, ranging from stimulus enhancement (increase in attention of an individual for an object because another individual pays attention to this object) to imitation (an individual imitates the exact behaviour of another individual to achieve a desired goal). The social learning process occurring in this experiment is probably observational conditioning. Observational conditioning, often associated with social learning of predator recognition, is a form of Pavlovian conditioning in which the response of the demonstrator acts as an unconditioned stimulus that elicits a matching response on the part of the observer (Emery & Clayton 2005). However, more testing is needed to ascertain this hypothesis. Predation is an important selective force, acting on the morphology, behaviour and life history of prey species (Lima & Dill 1990; Chivers et al., in press). Prey often face a trade-off between predator avoidance and fitness-related activities such as foraging, territorial defence and reproduction. An obvious prerequisite for prey to respond appropriately to predators is to be able to recognize their predators as a threat (Mathis et al. 1996; Ferrari et al. 2007b). Social learning provides an effective mechanism to acquire such recognition. Our research opens the possibility that social learning is widespread in taxa that have been traditionally considered less social and also that prey guild members in mixed-species assemblages can learn from each other. Studying learned predator recognition is of particular importance in amphibian species. One of the reasons put forwards for the global decline of amphibian populations is their inability to cope with introduced competitive or predatory species of fish and amphibians (Gamradt & Kats 1996; Blaustein & Kiesecker 2002; Blaustein & Bancroft 2007). More work is needed to investigate whether amphibians have similar predator-learning abilities as other vertebrates. In particular, researchers should focus on the limitations (both spatial and temporal) of learned predator recognition in amphibians, which could partly explain why some species seem to be particularly vulnerable following the introduction of new predators. Acknowledgments We thank Jean and Glen Chivers for their help and support and for letting us once again invade their wetlands for the duration of our field season. We also thank Dr David Stephens for his statistical advice. Research funding was provided to F. Messier and D.P.C. through the Natural Sciences and Engineering Research Council of Canada. All work reported herein was in accordance with the Guidelines to the Care and Use of Experimental Animals published by the Canadian Council on Animal Care and was conducted under the University of Saskatchewan Committee of Animal Care and Supply protocol no. 20060014.

FERRARI & CHIVERS: SOCIAL LEARNING IN FROG ASSEMBLAGES

References Blaustein, A. R. & Bancroft, B. A. 2007. Amphibian population decline: evolutionary consideration. Bioscience, 57, 437e444. Blaustein, A. R. & Kiesecker, J. M. 2002. Complexity in conservation: lessons from the global decline of amphibian populations. Ecology Letters, 5, 597e608. Chivers, D. P. & Mirza, R. S. 2001a. Predator diet cues and the assessment of predation risk by aquatic vertebrates: a review and prospectus. In: Chemical Signals in Vertebrates. Vol. 9 (Ed. by D. A. Marchlewska-Koj, J. J. Lepri & D. Mu ¨ ller-Schwarze), pp. 277e284. New York: Plenum. Chivers, D. P. & Mirza, R. S. 2001b. The importance of predatordiet cues in the responses of larval woodfrogs to fish and invertebrate predators. Journal of Chemical Ecology, 27, 45e51. Chivers, D. P., Zhao, X., Brown, G. E., Marchant, T. A. & Ferrari, M. C. O. In press. Predator-induced changes in the morphology of a prey fish: the effects of food level and temporal frequency of predation risk. Evolutionary Ecology. doi:10.1007/s10682-007-9182-8. Curio, E. 1988. Cultural transmission of enemy recognition by birds. In: Social Learning: Psychological and Biological Perspectives (Ed. by T. R. Zentall & B. G. Galef Jr), pp. 75e97. Hillsdale, New Jersey: L. Erlbaum. Curio, E., Ernst, U. & Vieth, W. 1978. Cultural transmission of enemy recognition: one function of mobbing. Science, 202, 899e901. Duellman, W. E. & Trueb, L. 1994. Biology of Amphibians. Baltimore: Johns Hopkins University Press. Dugatkin, L. A. & Godin, J.-G. J. 1992. Reversal of female mate choice by copying in the guppy (Poecilia reticulata). Proceedings of the Royal Society of London, Series B, 249, 179e184. Emery, N. J. & Clayton, N. S. 2005. Animal cognition. In: The Behaviour of Animals: Mechanisms, Function, and Evolution (Ed. by J. J. Bolhuis & L.-A. Giraldeau), pp. 170e196. Malden, Massachusetts: Blackwell Scientific. Ferrari, M. C. O., Trowell, J. J., Brown, G. E. & Chivers, D. P. 2005. The role of leaning in the development of threat-sensitive predator avoidance in fathead minnows. Animal Behaviour, 70, 777e784. Ferrari, M. C. O., Messier, F. & Chivers, D. P. 2007a. First documentation of cultural transmission of predator recognition by larval amphibians. Ethology, 113, 621e627.

Ferrari, M. C. O., Gonzalo, A., Messier, F. & Chivers, D. P. 2007b. Generalization of learned predator recognition: an experimental test and framework for future studies. Proceedings of the Royal Society of London, Series B, 274, 1853e1859. Galef, B. G., Jr & Giraldeau, L.-A. 2001. Social influences on foraging in vertebrates: causal mechanisms and adaptive functions. Animal Behaviour, 61, 3e15. Gamradt, S. C. & Kats, L. B. 1996. Effect of introduced crayfish and mosquitofish on California newts. Conservation Biology, 10, 1155e1162. Griffin, A. S. 2004. Social learning about predators: a review and prospectus. Learning & Behavior, 32, 131e140. Griffin, A. S. & Evans, C. S. 2003. Social learning of antipredator behaviour in a marsupial. Animal Behaviour, 66, 485e492. Herzog, M. & Hopf, S. 1984. Behavioral responses to speciesspecific warning calls in infant squirrel monkeys reared in social isolation. American Journal of Primatology, 7, 99e106. Hokit, D. G. & Blaustein, A. R. 1995. Predator avoidance and alarmresponse behaviour in kin-discriminating tadpoles (Rana cascadae). Ethology, 101, 280e290. Kiesecker, J. M. & Blaustein, A. R. 1997. Population differences in responses of red-legged frogs (Rana aurora) to introduced bullfrogs. Ecology, 78, 1752e1760. Lima, S. L. & Dill, L. M. 1990. Behavioral decisions made under the risk of predation: a review and prospectus. Canadian Journal of Zoology, 68, 619e640. Mathis, A., Chivers, D. P. & Smith, R. J. F. 1996. Cultural transmission of predator recognition in fishes: intraspecific and interspecific learning. Animal Behaviour, 51, 185e201. Vieth, W., Curio, E. & Ernst, U. 1980. The adaptive significance of avian mobbing. III. Cultural transmission of enemy recognition in blackbirds: cross-species tutoring and properties of learning. Animal Behaviour, 28, 1217e1229. Vilhunen, S., Hirvonen, H. & Laakkonen, M. V.-M. 2005. Less is more: social learning of predator recognition requires a low demonstrator to observer ratio in Arctic charr (Salvelinus alpinus). Behavioral Ecology and Sociobiology, 57, 275e282. Ward, P. & Zahavi, A. 1973. The importance of certain assemblages of birds as ‘information centers’ for food finding. Ibis, 115, 517e534.

1925

Cultural learning of predator recognition in mixed ...

final acceptance 26 October 2007; published online 15 April 2008; MS. number: A10807). Animals that live in social ... However, the degree to which social learning influ- ences behaviour in other taxa ..... Griffin, A. S. & Evans, C. S. 2003.

176KB Sizes 0 Downloads 213 Views

Recommend Documents

Differential retention of predator recognition by juvenile ...
Here, we investigated if the memory window associated with learned recognition of predators by juvenile rainbow trout was fixed or variable. Specifically, we.

Generalization of learned predator recognition: an ...
May 22, 2007 - 5 ml of either alarm cues or dechlorinated tap water and. 20 ml of lake trout ... of fishes on either change in shoaling index (c4. 2. Z3.7,. pZ0.44) ...

Differential retention of predator recognition by juvenile ...
(1 Department of Environmental Science and Policy, University of California, Davis, CA,. 95616 USA; 2 Department of Biology, ... Also available online - www.brill.nl/beh ..... species to identifying 'classes' of predators. In other words, their ...

amphibians Latent inhibition of predator recognition by ...
Dec 4, 2008 - Receive free email alerts when new articles cite this article - sign up in .... in response to predation cues, hence a line was drawn in the middle.

Threat-sensitive generalization of predator recognition ...
May 27, 2009 - These results support previous results by Mirza et al. (2006), whose .... Predator Recognition Continuum Hypothesis proposed by. Ferrari et al.

SINGLE-CHANNEL MIXED SPEECH RECOGNITION ...
energy speech signal while the other one is trained to recognize the low energy speech signal. Suppose we are given a clean training dataset X, we first perform ...

Learning in the Cultural Process - Semantic Scholar
generation, then could a population, over many generations, be .... But we can imagine that, over time, the community of people .... physical representations) into one bit string that can be applied to .... Princeton: Princeton University Press.

Predator Management in Utah - Utah Division of Wildlife Resources
Jan 24, 2012 - wildlife officials may choose to implement predator-management plans. The DWR recently updated its policy on predator management to place ...

Semi-supervised learning for character recognition in ...
Jul 31, 2013 - TU Dortmund University, Department of Computer Science, Dortmund, ... 1. Introduction. After several thousand years of human history and roughly ...... In 2008 he was awarded with a Ph.D. degree in Computer Science from ...

The role of latent inhibition in acquired predator ...
tween the two cues. For example, Chivers et al. (1996) dem- .... to the non-normality of the line cross data, we conducted nonparametric Mann–Whitney U tests to ...

Action and Event Recognition in Videos by Learning ...
methods [18]–[20] can only adopt the late-fusion strategy to fuse the prediction ... alternatively adopt the early fusion strategy to form a lengthy ...... TABLE III. TRAINING TIME OF ALL METHODS WITHOUT USING PRIVILEGED INFORMATION ON THE KODAK DA

Evaluating Cultural Learning in Virtual Environments
the requirements for the degree of Doctor of Philosophy. January 2006 ...... Hospitals have adopted VR techniques for pain management. (Lockridge, 1999), and ...

Predator Panic.pdf
“To Catch a Predator,” Dateline reporter Chris Hansen claimed that “the. scope of the problem is ... Main menu. Displaying Predator Panic.pdf. Page 1 of 9.

Machine Learning & Pattern Recognition
The Elements of Statistical Learning: Data Mining, Inference, and Prediction, ... Python for Data Analysis: Data Wrangling with Pandas, NumPy, and IPython.

Sparse Distance Learning for Object Recognition ... - Washington
objects, we define a view-to-object distance where a novel view is .... Google 3D Warehouse. ..... levels into 18 (0◦ −360◦) and 9 orientation bins (0◦ −180◦),.

Learning Personalized Pronunciations for Contact Name Recognition
rectly recognized, otherwise the call cannot be initialized or is ... tain very few words, for example, “call Jennifer”. ..... constructed in the same way as in [3].

Svensen, Bishop, Pattern Recognition and Machine Learning ...
Svensen, Bishop, Pattern Recognition and Machine Learning (Solution Manual).pdf. Svensen, Bishop, Pattern Recognition and Machine Learning (Solution ...

Mixed strategies in games of capacity manipulation in ... - Springer Link
Received: 30 September 2005 / Accepted: 22 November 2005 / Published online: 29 April 2006 .... (2005) report that many high schools in New York City .... Abdulkadiro˘glu A, Pathak PA, Roth AE (2005) The New York City high school match.

Cultural Change as Learning: The Evolution of Female ...
possess private information about the long-run costs of working (e.g., about the ... models in which changes in women's wages affect female LFP solely by ...