Table 2 Acoustic characteristics (mean ± sd) of the calls of juvenile crocodilians in function of body size.

From: Size does matter: crocodile mothers react more to the voice of smaller offspring

Number of recorded individuals (mean number of calls per individual, min-max)

Size category

20 – <40 cm

40 – <60 cm

60 – <80 cm

80 – <100 cm

100 – <120 cm

American alligator (19 calls/individual, 10–20)

31

1

23

15

6

Spectacled caiman (12 calls/individual, 5–20)

5

3

1

–

–

Nile crocodile (12 calls/individual, 3–20)

18

17

11

13

1

Morelet’s crocodile (19 calls/individual, 16–20)

–

4

1

–

–

Orinoco crocodile (7 calls/individual, 1–19)

1

1

10

1

1

mean pitch (Hz)

 American alligator

593 ± 83

418

461 ± 70

459 ± 73

405 ± 55

 Spectacled caiman

376 ± 49

383 ±  75

358

–

–

 Nile crocodile

456 ± 93

416 ± 58

412 ± 51

389 ± 47

222

 Morelet’s crocodile

–

413 ± 67

377

–

–

 Orinoco crocodile

432

405

433 ± 70

402

413

start pitch (Hz)

 American alligator

1100 ± 179

823

1128 ± 239

1092 ± 219

926 ± 200

 Spectacled caiman

485 ± 98

665 ± 195

658

–

–

 Nile crocodile

596 ± 135

480 ± 64

463 ± 67

375 ± 57

321

 Morelet’s crocodile

–

732 ± 148

603

–

–

 Orinoco crocodile

608

652

690 ± 172

476

770

max pitch (Hz)

 American alligator

1117 ± 183

893

1135 ± 233

1094 ± 217

929 ± 198

 Spectacled caiman

553 ± 77

678 ± 192

658

–

–

 Nile crocodile

635 ± 141

502 ± 65

508 ± 61

439 ± 49

351

 Morelet’s crocodile

–

821 ± 226

671

–

–

 Orinoco crocodile

623

657

730 ± 153

671

790

min pitch (Hz)

 American alligator

290 ± 36

147

161 ± 21

149 ± 30

144 ± 19

 Spectacled caiman

187 ± 28

170 ± 15

179

–

–

 Nile crocodile

316 ± 98

339 ± 68

308 ± 69

311 ± 49

133

 Morelet’s crocodile

–

170 ± 15

176

  

 Orinoco crocodile

231

268

269 ± 40

221

231

end pitch (Hz)

 American alligator

292 ± 37

150

166 ± 19

153 ± 30

150 ± 21

 Spectacled caiman

187 ± 28

171 ± 15

184

–

–

 Nile crocodile

318 ± 102

343 ± 69

316 ± 73

326 ± 56

136

 Morelet’s crocodile

–

172 ± 18

176

–

–

 Orinoco crocodile

231

269

277 ± 40

244

239

maximal frequency (Hz)

 American alligator

785 ± 182

474

538 ± 63

475 ± 59

442 ± 43

 Spectacled caiman

1401 ± 679

706 ± 126

511

–

–

 Nile crocodile

2671 ± 1192

2648 ± 907

2165 ± 495

1894 ± 257

1140

 Morelet’s crocodile

–

2546 ± 78

2339

–

–

 Orinoco crocodile

3186

2048

4050 ± 314

1870

1657

Q25 (Hz)

 American alligator

705 ± 92

435

447 ± 54

393 ± 60

353 ± 28

 Spectacled caiman

1056 ± 289

618 ± 38

478

–

–

 Nile crocodile

1615 ± 530

1707 ± 573

1523 ± 350

1609 ± 219

920

 Morelet’s crocodile

–

1826 ± 46

1741

–

–

 Orinoco crocodile

2455

1656

1767 ± 251

1457

1491

Q75 (Hz)

 American alligator

1377 ± 165

980

1172 ± 232

960 ± 168

934 ± 160

 Spectacled caiman

2277 ± 493

1804 ± 152

1080

–

–

 Nile crocodile

3317 ± 761

3115 ± 666

2728 ± 496

2714 ± 252

2110

 Morelet’s crocodile

–

2982 ± 161

2917

–

–

 Orinoco crocodile

3484

2369

2737 ± 311

2196

2543

IQR (Hz)

 American alligator

672 ± 168

546

727 ± 198

567 ± 127

582 ± 139

 Spectacled caiman

1221 ± 293

1186 ± 165

601

–

–

 Nile crocodile

1701 ± 484

1408 ± 279

1204 ± 233

1105 ± 310

1191

 Morelet’s crocodile

–

1156 ± 128

1176

–

–

 Orinoco crocodile

1029

713

971 ± 216

739

1052

cent (Hz)

 American alligator

1164 ± 106

958

1035 ± 120

884 ± 108

863

 Spectacled caiman

1766 ± 330

1377 ± 69

1009

–

–

 Nile crocodile

2490 ± 540

2448 ± 519

2187 ± 338

2161 ± 159

1555

 Morelet’s crocodile

–

2429 ± 102

2366

–

–

 Orinoco crocodile

2897

2084

2269 ± 232

1988

2075

skewness

 American alligator

2.03 ± 0.07

2.52

2.29 ± 0.48

2.56 ± 0.45

2.87 ± 0.57

 Spectacled caiman

1.63 ± 0.45

2.21 ± 0.13

2.43

–

–

 Nile crocodile

1.40 ± 0.34

1.58 ± 0.50

2.05 ± 0.48

2.52 ± 0.36

2.37

 Morelet’s crocodile

–

1.47 ± 0.19

1.67

–

–

 Orinoco crocodile

2.20

2.63

2.19 ± 0.62

2.18

3.03

kurtosis

 American alligator

6.81 ± 2.25

8.50

7.88 ± 2.72

9.22 ± 2.52

11.30 ± 4.48

 Spectacled caiman

5.75 ± 2.00

7.80 ± 0.64

8.35

–

–

 Nile crocodile

4.87 ± 1.41

5.56 ± 2.19

7.69 ± 2.43

10.24 ± 2.08

9.62

 Morelet’s crocodile

–

4.80 ± 0.69

5.66

–

–

 Orinoco crocodile

8.62

10.63

8.21 ± 3.92

7.57

12.6

sfm

 American alligator

0.385 ± 0.074

0.401

0.430 ± 0.070

0.345 ± 0.065

0.355 ± 0.074

 Spectacled caiman

0.568 ± 0.059

0.553 ± 0.047

0.374

–

–

 Nile crocodile

0.734 ± 0.072

0.721 ± 0.065

0.691 ± 0.066

0.629 ± 0.065

0.562

 Morelet’s crocodile

–

0.721 ± 0.055

0.736

–

–

 Orinoco crocodile

0.600

0.520

0.607 ± 0.068

0.555

0.647

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